I've stripped the paint first. My first Model T roadster still had the 1916 Ford paint on it, when I started sanding it off years ago with a 1/4 in drill with a sanding disc, the paint just melted and started flowing like I was melting plastic. I worked on the hood of the old 1951 tractor but the paint was 95 % gone, and it still takes a long time to work it out but I was using a 5 in disc made from a SS plumbing clean out cover I bought at lowe's . Metalmeet forums show how to build one for a 7-9 in grinder. sometime I'll try for a big one.