[salty]

Glass, a razor blade should work.

Mineral spirits on the plastic might soften the paint. Dilute Acetone 50/50 with water and try it on a corner of the the plastic, after the mineral spirit soak. The Acetone mix will damage the plastic if left on too long. Wipe on see if it removes the paint and then wipe it off. Do it as soon as possible as the paint will harden cure very quickly.

You can also get good results with SEM plastic paint to repaint the panels. The color match is usually good. There are some posts in the pro section on the proper use the the paints.