Great ideas and I'll definitely have to try the Mr. Clean eraser. I want to change the road numbers on a Lionel scale F-3 without damaging the paint, which is a strong point of these locos IMHO. I'm only using the shell on a P&D or possibly a Protocraft drive.
I used the 3M Polishing Papers that Old Goat mentions removing the paint from the "A" unit windows of my GGD E7 and it worked like a charm. Nothing would remove this paint so I had to sand it off with the coarser paper and then polished the windows with successively smaller Micron papers. When I was done they looked like new, just no paint.
A great hobby tool for the workbench indeed.
Butch