I know nothin about guitars or what might effect the sound quality, But I think I would start with a high to med build urethane sealer primer, you can get it in a spray can at the automotive paint stores to save some money you wouldn't much. slick sand is a good one, it is made by evercoat
sand it with a block or sand paper wrapped around a paint stick starting with 220 and working to 400 or 600 grit.
this will save time and paint, you will have a much better, slicker base to start painting on and the urethane primer will work and sand much easier than the paint in question
Mark