It has been a slow progress but my wife and I have played to the point that pain and pleasure are intertwined and her body reacts in ways she cant control.
For starters it helps when both involved are into the same results. Pain play needs to be taken slowly over time. Being in bondage on the receiving end helps as it reduces the chances of escape. Safe words are essential. Push the sub's pain tolerances a little bit consistently all the time and reward your sub with an orgasm and lots of aftercare. Good luck and best wishes!
There are two key things in this advice. The first is having a safe word. That is essential and must be recognized or things can turn for the worse. The other is aftercare. This is most important due to the intensity of the experience. I always give my partner aftercare even if all we did was have sex. I do it as much for her as for me. It is a very enjoyable part of a session as I get to hold and appreciate my partner for giving me such pleasure.
Ever do one of those clothespins zippers? Couldn't be as painful as caning, or could it? I've no idea, as I've only watched it on a vdo.
It depends as you can get different types of clothespins zippers. I've used rubber tipped ones as a sub and the pain level is just right, it is just barely tolerable and a constant pain. Depends where they're place too! They are a great addition to bondage if, like me, you enjoy being fully restrained head to toes in various restraints. You can get different tipped ones, coarse sand ones are very painful, even fine sand ones I dislike. They doesn't compare to caning because that's a short intense level of pain. They leave marks but nothing like welts from a cane or evil stick.
Caning is an art and it's difficult finding a canvas to practice on. Depending on the position and the gender of the person receiving the cane, it can be easy to miss the spot where you want to inflict the discipline. I hate leaving public marks but a well placed cane can make her think about it for hours.