Fiberglass is commonly painted using gel coat, which consists of fiberglass resin that is pigmented with color. Gel coat is a very strong and durable paint that acts as a protective layer over the fiberglass as well as paint. On some applications primer is used under the gel coat, but it's not required on all fiberglass applications. Gel coat is a very thick paint that requires a gel coat spray gun for application. All gel coating materials and supplies can be found at your local marine supply store.
Put on a respirator and use coarse-grit sandpaper to sand the surface of the fiberglass that will be gel coated. If the area is large you can use an electric sander. Lightly scuff the entire surface until it is smooth and flat.
Blow all the dust off of the sanded area and then clean it thoroughly using acetone on a clean rag.
Tape off any areas surrounding the fiberglass using painter's tape. This will prevent any unwanted over spray.
Add the fiberglass primer to the spray gun and apply an even coat covering the entire surface. Keep the tip of the spray gun at least 1 foot away from the surface to avoid any runs. Let the first coat dry and spray a second coat of primer onto the fiberglass. Let the primer dry.
Mix the fiberglass gel coat with the hardener following the recommendations on the containers. Use a small bucket and a stir stick to thoroughly mix the gel coat. Add the gel coat to the gel coat gun following the directions in the manual.
Apply the first coat of gel coat in a heavy mist. Apply the gel coat as evenly as possible for the best results. Let the first coat begin to get tacky and then apply the second coat of gel coat. The second coat should solidly cover the surface. Let the gel coat harden.