Pink pencil eraser is the tool of choice here.

Q-tips and alcohol are uses to clean the contacts if I can't disassemble the cart. I use 100% isopropyl alcohol that is available at Fry's.

Formula 409 is my cleaner of choice for gunk on a cart or on the edge connectors. Rinse well with clean water or alcohol.

For permanent marker I use the pure 100% isopropyl alcohol and a toothbrush or rag. If that doesn't work then I use a fresh marker to go over the old THEN use the alcohol to remove both.