right now im currently in the process of sanding my acoustic guitar down to the original wood. it was originally an epiphone black just normal dreadnought acoustic but i actually am going to sand it all the way down to the wood then have my friend draw a really cool design on it. i was just wondering what he should use as far as paints, pencils, pens and so on? i dont really know if it matters or not. just wondering if any are bad for the wood or not. and i wanted to know what to do after hes done, just put a coat of lacquer or what? thanks in advance if you can help.
Well if you want it as a natural finish, I would keep going with how you're going, but as you get nearer to the wood, raise the grit of the sandpaper tp about 400-800, higher if you have it.

If you're painting it another colour, you don't need to go all the way down to the wood, simply get all the clear coat off. Use guitar paint spray cans or, an easier method, use Auto paint, which is what I'm using for my build atm. Use very light mist coats at first, then get slightly heavier, but still be very light.

As for drawing, I'm not an expert, but I would consider going to the Ultimate Painting and Refinishing Thread if I were you, there is a more comprehensive covering of things there. They also cover clear coating in greater detail.
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Get a sheet of adhesive paper if you can, and get him to draw on that, then once you've finished and you want your design to be on the top coat, use a sketching knife to carve out the design, make sure the adhesive paper blocks off all but the design and just spray over the design..

when you take the paper off you should have your guitar as before but with a decal there. Leave it a day or so and lacquer it then let it cure a while

all day enjoy