Remove any loose or broken pieces from the area to be repaired. If necessary, cut a hole completely around the damaged area. This will ensure a complete repair.
Remove any wax or mold release from the area by wiping with paint remover or acetone.
Use 80-grit sandpaper to "rough" the area around the repair. This ensures that the resin sticks to the area. Remove sanding dust with a dampened cloth. Allow the area to dry thoroughly.
Cut the fiberglass cloth to a size about 3 inches larger than the area to be repaired.
Roll a thin coat of the resin/hardener mixture onto the surface where the cloth will lie.
Roll the resin mixture into the cloth. Begin at the center and work toward the edges. It is fully saturated when it becomes transparent. Use a squeegee to remove any bubbles.
Allow the resin to partially cure. Keep a close eye on it. Heat and humidity will affect the curing time.
Before the resin is completely cured, add a second coat. Many thin coats are better than fewer thick coats. After the final coat is applied, allow it to cure overnight.
Sand the fiberglass repair to match the surrounding area. The repair is now ready for a coat of paint.