12-16-2025. Drum Sander. I have been advised to use a drum sander, as it is easier on the sheet metal than a flap disc on an angle grinder. Well, yes it is! However, even at 40 grit, I finished the roof, started on a rocker and a few other spots and wore that drum half way out! Pics follow, you can see the difference comparing both methods side to side. I also took a couple pics to show how it will look ran over with a DA on 80 grit to prep it for filler. DUSTY! closer to starting the blocking.