Honestly - don't do it in your ass. The whole deal with actually turning around far enough to pinch your ass in the first place gets you breathless and worked up. Do what I do - sit down, relax, and pin yourself in your quad. Believe me, it's much easier than you think and you're not stressed out by all the turning, pinching, aspirating, plunging etc etc.
Good luck dood. Deep breaths.