 After the surface is dry, you may notice some old paint that's peeling and flaking, so be sure to scrape and sand that away. Any bare wood should be primed before painting so the top coat will adhere much better. Plus, some primers also help keep mold and mildew from returning. After the primer dries, fill in any gaps or cracks with caulk to keep out moisture, dirt, and the occasional critter or insect.