anyone have bondo tips?

I find it best to do light coats rather then heavy. Also just as its about to full harden is the best time to start working it. They do saying not to use cardboard as a mixing board because it does some soak up some of the resins in the filler. Go slow and make smooth strokes 1 direction. There are some good youtube videos on how to mix filler. Watching a few of them could definitely help. They can show you the correct techniques so that you're getting a good layout with the filler. Make sure you fold it when you're mixing it and not just stirring around otherwise you get air bubbles in the filler