I might be dumb too, but the roof and fender tops and bed rail tops of my first old truck received hours of sanding with a coarse grade of sandpaper on a DA, in some cases a high speed air grinder with a flex wheel to get the pits out, the metal was plenty thick and pitting wasn't too bad. Got it all shiney and then primered with DP40. Like Kool . . . never had a problem with rust after that.
