I've never tried the wax. I have tried heat, PD rust blaster, and other stuff. The tighten then loosen also works to an extent. I'd do all three. Sometimes, I drill a hole through the bolt. This adds heat, the metal can colapse, also you can spray into a blind hole. Its a last resort though. I hear Kroil is the king of rust penetrants. Impacts sometimes do a better job than breaker bars. I had two harmonic blancer bolts on different cars, that were a pain. A good impact wrench (Snap-On) did the trick.
Tom