Originally posted by cartersbs
Be carefull with the torch, I've seen a lot of warpage from people using this technique. I like to grind as much as I can and then media blast the last bit to really get the nooks and crany's cleaned out, madia blasting must be done carefully as well to prevent heat build up.
He won't have to worry about this... All you have to do is pass over the bondo a FEW times and it should start breaking up and getting powdery like shine said. After that, get a scraper and 80 grit sand paper and take the rest off and smooth the metal.