Tools and how to start

I usually use a da sander and start with 40 grit if the rust is deeper.Then I move up to 80 grit and hit it with epoxy primer.Then hi build primer over that,block sand with 180 to cut the primer surface then move up in grits to at least 320,prefer 400 before paint.Dont break through to bare metal.If you do it has to be primed.

Worked in a few body shops,so just ask away!