What would you recommend for a finish to use on a wood clipboard? I know there are "tough" finishes, and "durable" finishes, but in this case, I'm specifically looking for something that can best resist a ball point pen. Ideally the clipboard would be used with a pad of paper, but it would be nice if it could also hold up to a ball point pen when the clipboard has just a sheet or two of paper in it. I don't expect to find a truly impervious finish, but I'd like to know what some of the best options are. I'm either brushing or wiping on the finish, but spray in a rattle can would be OK.