I bought an old Dragon Ball Shitajiki/Pencil board, but I didn't notice in the listing it had a bunch of pencil scribbles and some graphite/pencil lead staining on it at some parts.

Anybody have an idea for how I can safely clean it?

I've been using a q-tip I've dipped in liquid dawn soap and soaked in water to try to rub graphite marks and stains out, and that has kinda worked, but it still leaves some of it left in some spots. Could I try rubbing alcohol or will that likely eat into the plastic or the printed artwork?