Well living in a really hilly area of LA I've learned when you're going downhill you check your speed by skipping. Also if you're giong to go brakeless you should do so with a gear that you can easily control. Last Friday I did Critcal Mass brakeless and we went down quite a few pretty gnarly hills, I felt fine, at no point did I spin so fast I couldn't bring myself under control, then again I run 41x14. If you're having probs and you're spinning out of control you might want to look into dropping your gearing.

Then again if you don't usually hit hills, I guess the point is moot. *shrugs*