This is a tough call. I am a dom crossdresser and have been called upon to do this. It requires a lot of knowledge of the penis as to what it can take without damage. A whip flicker is the best instrument to use in that you can control the amount of power to be used on the shaft which can take more and the head which takes less. Your best bet is to get your friend to tie your cock separately with your balls and then hang you on your toes to a door knob as your friend wallops your ass with a flat paddle that will make your ass red to purple but not with the stripes of a whip. Hope this helps emma