Use zero rust on frames and such where you are not concerned with how smooth the finish is. If I'm right, the best way to apply this stuff is to just "cuff" the loose stuff with a wire brush off and slather it on. That's the beauty of it. Used it on a bumper and grill for my brother in laws 54 and it's starting to get dull already. On about 6 months. Wouldn't do that again.
I ALWAYS use it on the insides of fenders and such too.
see ya
Jim
