First and foremost I am a bass player as opposed to 6 string guitarist. I am better at it, more comfortable with it, and like putting a thump if folk's chests. Long story short, I have been asked to lay down some guitar leads over about 3 songs. I have the tracks handy but i have to be ready in like a day and a half. I do have really good guitar gear and such is that they may have thought I could play said gear. I can play it, but nowhere near my bass level of skill. The good thing is I am only going to be laying in a few chords here and there, for the most part its all lead/solo. Here is the question. I had some scales in mind. If I wanted to mark some spots (a good few rather), on one my practice guitars (which even those are quite nice) - could I use a white grease pencil and get away with just cleaning the fretboard after a few days. This will help me, but I don't want to ruin anything. I was thinking of some bits of painters tape but that's too labor intensive and I got to get goin on this. What'cha all think.