After 50 or so years, the switch on my wheel had turned into sort of a rubberized concrete. One layer came up easy (about 1/16" worth), but the rest seemed almost permanent.
I ended up using a Dremel with a wire wheel (make sure you do this outside or you'll spend hours cleaning your garage DAMHIK), then digging the rest with an Xacto.

While outside on the turnpike They got this new hit tune Where thrills become as cheap as gas And gas as cheap as thrills