Just from personal expierence, try Acetone seems to remove just about anything. Be careful though, I'm thinking the acetone might eat through the plastic, if it is plastic. Test it somewhere before using it one your faceplate. An tottaly off the top of my head, I've used simple green for just about anything. I keep a bottle in my car just in case. Try some simple green too, not quite as strong as acetone, but it can clean damn well.