Couple of ideas:
(All have been tested, so no matter how mad they may sound, they do actually work!

)
First, for straight flogging, use electrical wire. And instead of reaching back and trying to hit your butt, swing to the side in front of you, and let the wire curl around your hip.
The tip then gains speed as it curls around, meaning that even soft blows has a fair effect.
Doesn't completely remove the 'fear-factor' of self-flaggelation, but it does mitigate it.
Second, use a crotch-rope with rubber-bands tied to it.
The idea is first attaching the rubberbands to a fixed point, then you pass the rope through 'em, and tie it on.
Finally, cuff yourself in front with the cuffs passed through the crotch-rope.
Now, all you have to do is get the key which is on the other side of the room. As you move forward the rubberbands will break, and snap back on the rope.
Just don't do anything stupid such as using so many rubberbands that you can't break free. *g*
As always, test the rig first.
Third, for CBT there's a variation of dropping a book (too inaccurate IMO).
Use a cardboard tube. Like the ones you get posters in.
Sit down on the floor with your legs spread, place tube vertically on your balls, insert appropiate weight at other end, and let go.
That sound of a sliding weight you get for a second, is enough to make you cringe after a while.
Finally, for those amongst us who have trouble pulling nipple-clamps off when instructed to....
Simple solution.
1) Attach clamps with a string between them.
2) Tie handcuff key to string.
3) Tie 3ft of rope to string, and tie cuffs to other end.
4) Pass rope between legs, and lock cuffs behind back.
5) Want the key? All you have to do is pull on the rope.
The thing I love about this one is that while you wait, mustering up the courage, the nipples just keep getting more and more sensitive.
Just don't do anything moronic as using clover-clamps, or any other self-tightening devices.
CheerfullyInsane