Picked up an old Bar-b-kettle for $5 on Craig's List. Really faded, rusted a bit as the porcelain was real thin in spots. Removed the handle and the vent and attacked it with my random orbit sander. Started off with a coarse grit, 80 or 100, and moved up to finer grits when the porcelain was gone. Primed and then painted it Red. looks great still 2 or 3 years later. Here is is before the first cook. It lives on a drum so does not see high grilling temps.
I'm thinking a grinder would be WAY too aggressive a tool for this project.
Oh yeah, wear a dust mask.