Repairing dull and scratched gelcoat
If the gelcoat has become dull, it is because UV-light, salt and water has leached the plastic, making it dry.
Dull surfaces and scratches are removed with Rubbing, a fine abrasive that easily and gently restores dull and scratched surfaces. For best result, use a rotary polisher with a hard polishing pad. Buff to remove possible swirls. In case of deeper scratches or very dull surfaces, wet sand with 2000-paper followed by 4000-paper. Continue with Rubbing afterwards.