^1 hit it pretty much on the head. Once you get the metal where you want it, go over the panel with whatever grit the epoxy primer manufacturer recommends, and apply the epoxy. The filler can be applied over the epoxy. If you have some minor rust, you can use Naval Jelly to remove it, clean the surface, sand with the right grit and epoxy.
BTW.. There is a post on removing rust that was done by Randy Ferguson. It is very detailed, and he is a metal working master.