[UncleJimmi]

I have always preferred to use a pneumatic 6" DA sander that locks the pad in a grinder like mode. switch the lock and re-sand with the same grit, that will remove the ledge created from switching directions (end of stroke) in the grinder mode.
When sanding with the pad locked you should see long curved lines and the pad should be almost flat to flat surfaces. The long sweeping lines make it easy to see the imperfections in the metal. When you unlock the pad you see lines that look the same as from a palm sander, these little overlapping circles hide imperfections like pits and other sanding lines.
I call the grinder mode DQ (Do it Quick) and DA stands for dual action.
I always use a belt grease to prevent galling of the metal, a little on the pad, and or, a little on the part. the heavier the grit the more the grease.
I usually use 120 DQ then DA, 220 DQ / DA, and 320 just DA, then buff.

WARNING{ deep ruts / heavy waves can be created quickly when grinding.
Since you can't put the pad completely flat, you should move in the direction of the lean / tilt. Use a practice piece.