So what is wrong with a DA and 36 or 40 grit, aside from dust everywhere?
Bill, why are they called "mop" disks? I think I have some, but have never tried them.
I think I like the bristle disks for cleaning rust out of pits. They come in 3 "grits", but seem sort of spendy. A wire brush will do the same thing, but I hate pulling the wires from my feet just cause I walked in the garage in socks or barefoot 2 weeks after using one despite cleaning up really well. I've had them imbeded in my shoulder too after laying on the garage floor.
Finally, I'd guess if you can load up the same disk from Woody's Wagner, into an angle grinder it would work as well, just probably heavier.
It's usally not the outside surface that's hard to strip. The inside or underside of my rear fenders was a pain because of the shape.