despooking and bombproofing...

Great posts chrisopher !

If you have a regular progression from natural aid to artificial aid, your horse will understand what it is that leads you to tap with a crop. I use soft leg, medium leg, hard leg, one cluck [i hate people who cluck constantly, obviously your horses doesnt care about your bird noises !], then tap with the crop. If you are consistant with your progression they will learn it, and learn what to do not to get hit. If you randomly hit them for no reason, ya they will probably fear you.

I also use a crop/bat, not a whip. Have you ever hit yourself with a crop ? It doesnt hurt, its more for the noise of leather slapping leather.

but then you get the lazy "to cool for school" ones that even with the progression go insanely mental when you finally do give them a tap with a crop... Mitchell. As if to say "OMG you did not just do that to me"

This is indeed the most effective way. Desensitizing at the barn helps and is fine to do if you don't have the time to get out, but there is no substitute for time on the trail and in the saddle.