it hurts at first because you're hitting virgin nerves that aren't used to stimulation. they over react to it and send pain signals to the brain.. but it only hurts for a few seconds. Once they get used to the stimulation... super intense orgasms. It takes a while but worth it
I love to do this to male sub slaves for long periods of time. Feeling a big hard cock pulsing in my hand as I edge it and hearing the slave moan and beg for release is such a turn on. I am looking for a live in slave at the moment who is willing to undergo orgasm training of this kind for many hours.