(Darryl) Let me say a little bit about our journey. My wife and I never did the Exchanges. We embarked on this path about 13 years ago, before Cupid's Poisoned Arrow was even written. We flew by the seat of our pants with some basic information from Taoist sources. We arrived at the karezza approach simply by feel and found Marnia's information afterwards.
It is still an evolving journey for us. I don't know if you ever "arrive". The core of our current practice is basically frequent, (pretty much every day) karezza-style love making. For us this mean slow, sensual intercourse without getting heated way up. Since we don't orgasm, the 'middle zone' is mostly where we play. We don't engage in typical genital foreplay, but instead start with cuddling and gentle affectionate touching.
When not in the bedroom, touching and more touching is our recipe for continued connection. We don't force the touching, but find that the frequent karezza lovemaking draws us towards regular touching. We also know that when we feel disconnected, the tendency it not to touch. So we'll use touch to help with reconnecting.
We find its important for us to engage sexually even if we're not in the mood all the time. Being non-orgasmic is part of the picture, but the regularity is equally important in maintaining the flow of the experience. This means creating space so the lovemaking doesn't get squeezed in between other things, which I know can be a challenge. Once the space is created and held it becomes easier to maintain. Since you've done the Exchanges (from Cupid's Poisoned Arrow), I assume a space is in place to some extent. If you can, morning is the best time for karezza.
I would say the essence of our experience during karezza is a kind of sending energy by me and a receiving energy for her, which we both find deeply satisfying and nurturing. If you have a solid sexual relationship then jumping into frequent karezza lovemaking goes pretty smoothly. Issues like porn, or being shut down physically and emotionally, can require a slower approach.