Let's say I want to mod my Fender Squier SSS Stratocaster to look better. The first thing that comes into my mind is the paint. In some places my Squier has some paint chips and signs of it getting hit. What you normally would have to do would be to get rid of the old paint using a sprayable epoxy or by just sanding it down (you can help yourself with a heat gun). Make sure to remove everything from the body before you do anything about the paint. You can further sand the body wood down with a not-so-rigid sandpaper after which you can fill the gaps in the body with wood dedicated polyester resin and its catalytic. Next you would have to let it dry and put it in a wood sealer afterwards. Then, use a sealer to softly move across the surface of the body a number of times. After the fifth coat of sealer, let the instrument body dry out for 3-4 days. After sanding down the sealer, you can use the polyester, polyurethane or nitrocellulose (which is more eco-friendly) to paint your wood. A coat of paint on the front and another on the back should do, but apply more if you have enough paint left. For 2-3 days you should let the body dry and get the rest of the parts cleaned. Spray laque on the instrument and let it dry for 2-3 weeks. Then polish it and mount everything back on.