I have a YHM upper that is marked for 6.8SPC. I've since bought a complete RRA 6.8. Wondering how to remove the white lettering without screwing up the finish too much? I mean, I could sandpaper it... just wondering if there's a trick, like using an alcohol wipe on sharpies, etc. Anyone? Will pain thinner/turpentine work? Essentially the same, I assume, as the T markings?