7. Mix the filler and hardener according to the instructions on the can. Using a thin, rubber-spreading card, begin applying thin "skim" coats over the fiberglass, making sure that some filler squeezes through the holes on the first coat. Feather the mixture onto the surrounding painted surface; the idea is to blend the filler onto the existing fairing without creating a rough edge, and to make the filler best resemble the origi-nal shape of the fairing. Oh, and by the way, you best hurry up-polyester filler is unspreadable after two minutes.