Sounded interesting, right? Well, now that I have your attention, I have to confess the question is rather mundane and about my bass. If I want to coat the maple fingerboard of my fretless with polyurethane (master gel), do I have to remove fully the Formsby's tung oil/varnis coating first? Or, can I just sand it lightly first and then start applying the layers of polyurethane? Thanks in advance for the help.