I actually just tried this out myself a little while ago... I couldn't quite get there because I cracked and went into a normal session. Still fucking awesome though. I'll definitely be trying again.
The experience left me with a thought and a little bit of a fantasy... I think this would work well for some bondage play. Hands and feet restrained, a partner teasing just the frenulum... add in a little dirty talk and I think it would work well. ... and now I'm forming an idea for a story... *scampers away to work*
*edit**returns* I forgot to mention, I was getting the best results with very gentle, slow movements. Almost no pressure even though I'm uncut. As for hand position, I had my thumb on top to help with what little pressure I did use while my index and middle fingers slowly circled the area. Didn't lose erection once.