Repairing nicks and dents in an electric or acoustic guitar can be a difficult process. Many guitarists regard dents and nicks as adding to the guitar's character. In fact, they have become so popular that major guitar manufacturers, such as Fender and Gibson, market and sell pre-aged guitars. It is now possible to buy a guitar that looks banged up and damaged just like Stevie Ray Vaughn's guitar. Nevertheless, there are a few repair tricks that acoustic or electric guitarists can learn to repair minor dents and nicks.
Sand down the area around the dent. Use 800-grit sandpaper and sand with the grain of the wood.
Fill the dent with wood filler. Press the filler into the dent with a putty knife, leaving a slight mound above the surrounding area. Wipe off the excess filler with a rag. Allow it to harden or skin over.
Sand the patch with an 800-grit sanding block. Sand it until the area containing the patch is level with the body of the guitar.
Refinish with touch-up paint. Find a acrylic spray paint that matches the color of the guitar. Protect the guitar by wrapping and taping the guitar body with newspaper. If the repair is close to the neck, protect the fretboard with newspaper as well. Cut a hole in the paper around the patched area. Spray the area and allow it to dry. Read the instructions on the spray paint label for the recommended drying time. A small area will typically take at least an hour to thoroughly dry.
Apply a second coat of spray paint, allowing it to thoroughly dry before using the guitar.
Clean and degrease the area. Use a clean cloth and guitar polish. Guitar stores sell various brands of guitar polish for acoustic guitars, but regular furniture polish will work as well.
Repair the dent in the finish with lacquer. Fill the dent with a drop of lacquer. Depending on the size of the dent in the finish, the lacquer may be applied with either a toothpick or a small brush. If it is a small dent, use the toothpick to drop the lacquer in place. Larger dents need to be brushed. Lacquer shrinks as it dries, which makes it necessary to repeat the process in order to fill the dent. Let the lacquer dry for a couple of hours and then apply another drop, allowing the lacquer to dry overnight.
Smooth and level the repaired area. Start with a razor blade. Wrap the blade with a piece of scotch tape to protect the finish of the guitar. When the lacquer hardens, it will leave a slight mound slightly higher than the surrounding area. Use the razor blade to level and smooth the patched area. Finish the leveling process with 800-grit sandpaper. Use a rubber eraser as a sanding block to sand out the marks from the sandpaper.
Apply mirror glazing compound. Start with #2 mirror compound and lightly apply the compound with a clean cloth. Start three or four inches away from the repair and rub with the grain of the wood blending the glaze with the finish. Continue the job with #9 compound and finish it with #7. Use a clean area of the rag, or use a different rag altogether, when switching to a different compound. Stop rubbing once the gloss returns. Avoid excessive rubbing, as this will damage the finish of the guitar.