I'm looking for suggestions on what kind of filler material to use to repair dents/dings in thin sheet metal before painting. I'm painting the door to a ice maker from my boat. It has some dings that need to be filled in. Last time I did this I used fiberglass. That was a bitch, because the fiberglass is very tough and hard to sand, while the door material is thin and flexible. So, if you try to sand it, the sheet metal flexes from pressure making it hard to sand and get smooth. I finally got it done ok, but it was a lot harder than it had to be.
So, what I'm looking for is a softer filler that can be used on metal. I thought of auto body compound, but I think this is similar to the fiberglass I used last time. Good for a tough fender where you can use a sander and apply pressure, not so good for this. There must be something between joint compound which won't work and fiberglass, which is just too damn hard. Any ideas?