Paint Removal?

I did exactly what you are proposing. I used Acetone and it did not harm my black anodized aluminum.

If you want to test, go to an obscure area and dab the metal with a Q-Tip saturated with Acetone. If you see no harm, go for the paint.

Other chemicals that may help are Methyl Ethyl Ketone, Lacquer thinner and a cleaning product called Goof-Off.

how about a razor blade?

Maybe you can take a q-tip and put a little paint remover on a part of the preamp you can't see and see what happens. I'm sure other people will have better idea's