I am restoring an 73 Mach 1 and the doors have small patches where surface rust has occurred. I sanded off the top layers but it is pitted. SHort of grinding the pits off and risking thinning the metal, how can I remove these pits? Can I rust convert them and putty over that? Should I try to grind them out with a dremel tool? There are a lot of pits, some covering areas about 1.5 inches in diameter and the pits are think throughout the area.