A forum member shared this 2010 item with me. It's written by a Belgian named Philppe De Coster. Here's an excerpt, with his take on karezza:
Another way of experiencing spirituality in sex is by focusing on feeling in harmony and united with your partner on different energy levels. This is like a sexual meditation.
Before starting meditative sex you may not normally have much foreplay as you do not need a strong arousal but neither should you try to connect without any stimulation of sexual energies. However, the emphasis should not be on direct sexual stimulation but rather on expressing your affection for each other. After some caressing you may assume your chosen position. Comfortable positions for direct sexual contact are the sitting embrace shown above, or the ‘basic position’ ('scissor position') as described for Tantric Sex below. Facing each other in a close embrace while lying side to side is also suitable, whether with skin contact, or remaining clothed without being sexually connected if that is not appropriate.
Bring the tip of the penis in touch with the entrance of the vagina. Remain motionless in this position for some time while focusing on feeling the energy between you and especially where penis and vagina meet. To initiate or greatly increase the feeling awareness of pleasurable sexual energy, both partners may gently and rhythmically squeeze their buttocks or just contract the perineum. Coordinate each gentle pelvic contraction with an inhalation and with each other.
At the same time imagine or feel that the breath energy or prana is squeezed upwards to the top end of the spine. Hold the breath for a moment, and with the subsequent slow exhalation, imagine the prana again to fall down to the base of the spine. However, when you can feel the sexual energy itself as pleasurable streamings, you send this feeling to the top of the spine, and with each exhalation you feel it flowing out into your brain and down into your heart. Now you just continue to intensify the pleasurable feeling in brain and heart with or without moving further sexual energy to the top.
This method may be used as a complete meditation in itself and can even be done without a partner in order to learn to feel and work with the sexual energies. If and when you feel like proceeding to the next step, then either the male or female may gently rub the tip of the soft or hard penis up and down between the clitoris and the entrance of the vagina. If there is not enough natural lubrication, use oil or a lubricant jelly. When you feel ready, gently push the head of the penis inside. If the penis has remained soft, firmly enclose the shaft with your hand as in a fist and now the head can usually be inserted and further stimulated with some slow movements.
After penetration you may either remain completely motionless for some time or continue with the rhythmic pelvic contractions or start with karezza-like slow movements.
In Karezza the emphasis is on the inner feeling awareness as well as on the feeling of complete union with the partner. Orgasm is avoided or at least minimized. Caresses and slow controlled movements during intercourse generate a steady stream of sexual energy that is consciously converted into feelings of sublime joy and love. Typically, this may continue for an hour or more. It is not necessary for the penis to be erect or even inside to enjoy this type of lovemaking. Part or all of the time the tip of the penis may just touch the entrance of the vagina, or the sexual organs may not touch at all.
Initially concentrate awareness on the sensations at the point of contact with the partner, especially in the genital area but also wherever the skin or a caressing hand touches. This generates pleasant sensations, which can now easily be converted into a loving feeling. Open your heart and send this love to your partner. In a more active fashion you can in your imagination lead the energy felt in the genital or pelvic area upwards to the heart. There you feel it as love and radiate it out onto your partner, and also envelop both of you in a cloud of love.
You may also continue to contract the pelvic floor with each gentle thrusting or forward movement, and relax it during withdrawal. You do whatever feels best to generate a stream of sexual energy but without becoming too excited. Instead of feeling any excitement just in the sexual organs, focus on feeling it like a slow orgasm in the whole pelvic area, and especially in the pelvic floor or perineum. If you can feel the energies strongly, you may stop moving for a while and just focus on intensifying whatever you feel. Now you can radiate the energy not only throughout your own body but also onto your partner to produce a common field of sexual energy that envelops both of you.
When you have filled your brain and heart with pleasurable energy, move part of your attention to the spiritual love that you feel for your partner. Feel your heart expanding with a gentle love and add this to the cloud of pleasurable sexual energy that surrounds and interpenetrates both of you. Finally, without losing this special feeling, you now shift another part of your attention to the top of your head or to your crown chakra. By sending out some of the love you feel to your High Self or “God Presence Within” (you are your own God), you immediately receive an even larger amount of spiritual love back. Feel that both of you are now connected to the love and power of your higher or divine guidance. Feel united and in harmony with all levels of your own being as well as with your partner and with your spiritual source. Feel like melting into each other.
Initially try to hold all of these levels of connection with your partner in your awareness: the touching of the bodies, the pleasurable sexual energy in and around you, the love that you radiate onto each other as well as the feeling of both of you being connected, loved and protected by your divine guidance. Just bathe in this symphony of feelings or at times try to intensify certain aspects of it. However, after a while the sexual energy may go to sleep and then you just continue to remain aware of the love radiating from your heart, and the connection to your spiritual source. By prior agreement you may then also send love, harmony or healing energy to another target, be it to heal a situation, a person or the planet.
Depending on your previous ability to meditate and connect to these feelings it may be easy for you to experience the fullness of this union with your partner or it may take a lifetime to slowly getting there. It does not matter. The main thing is that it is a pleasurable way of moving in the right direction, of growing spiritually towards increasing awareness and harmony on all levels. It is not necessary that both have a similar level of experience. If one partner is much better able to contact the feelings of love and harmony, then this will help the other partner to come to these experiences easier and sooner than by meditating alone.
You can practice with different partners, and you can do it fully clothed, or with varying degrees of sexual contact. In this way it is possible for partners to have a pleasurable union on all levels even without any touching of the sexual organs if this is inappropriate. With a new partner or after a period of sexual abstinence, the sexual energy is usually so strong that it can be raised quite easily with a close embrace. When starting a sexual meditation relationship with a new partner or after a longer period of abstinence it may be good to start with a fully clothed embrace, and move to full sexual contact only gradually and perhaps in successive meditations.
For young or spiritually minded individuals who want to practice abstinence, meditative sex can be used as a satisfying outlet without suppressing sexual energies and causing emotional problems. It is also suitable for those who feel too old or low in energy or otherwise have lost interest in the conventional forms of lovemaking.
Even if the sexual energy sometimes cannot be aroused, meditating in a close embrace with a spiritual partner can still be a pleasant and satisfying experience. For many spiritual or sensitive individuals this sexual meditation may be more fulfilling than the more common forms of sex or lovemaking. However, sometimes, after a period of spiritual sex, one or both partners may feel a preference for a strong orgasm in order to relax more deeply. There are no fixed rules and you may use or alternate different forms of lovemaking as you please.
By stimulating sexual activity in a spiritual way without discharging the raised energy through an orgasm, the pelvic region remains permanently energized. This may occasionally lead to spontaneous low-grade orgasmic feelings, although generally the energy may appear to be asleep in-between sexual encounters. However, you can greatly increase the pleasure and benefit derived from any form of spiritual sex by keeping part of your awareness in the lower pelvis during daily activities. This tends to awaken the sleeping energy.
Understanding that there is a common experience in meditation and orgasm, as it has only been natural to combine the two. It begs the questions, why would you want too and what could it possibly add to the experience? The answer is, meditation will enhance your lovemaking tremendously by giving it your complete attention and full awareness, by being fully present in the moment.
The Kama Sutra, the ancient text of India is both an inspiring spiritual text and as the title is sometimes translated, “instructions on pleasure,” and is proof that meditation and sex have been successfully combined for all of human history.