If your car gets into any small scrape, any small scuff or damage to the paint can be ugly. This is especially true of any parts made of fiberglass like bumpers. You can touch up the paint on any damaged areas. But if you don't get the exact same paint color and use the proper painting method, the paint job can end up looking even worse. In some cases, repainting the entire fiberglass piece may be best. In those cases, apply the following steps to the entire surface instead of one part.
Get a can of paint the exact same color as that of the fiberglass part. If it's the original manufacturer's color, the paint code is on the parts tag located inside the trunk. Take that code to an auto parts store to find the exact shade you need,
Clean the entire fiberglass piece with a strong detergent (bug remover also works). If any area has tar patches, remove them with mineral spirits.
Sand down the damaged surface using 220-grit paper. Pick away any chips and scratches in the original paint. Scuff the surface up to 4 inches beyond the damaged area using a red Scotch pad.
Prime the surface with a primer surfacer, applying six light, even coats to the area. Wait for each coat to dry (the can should state how long it takes). Then wet sand the primed area using 600-grit wet or dry sandpaper. Scuff the primed surface with a grey Scotch pad.
Spray paint the surface using side-to-side strokes, starting at the top and working your way down. The top half of each pass across the surface should overlap the bottom half of the paint you applied in the last pass. Apply four to five even coats of paint using this process. Wait a few minutes between coats for the last one to partially dry. It doesn't have to completely dry before the next coat.
