If you want to paint vinyl door panels, you should know a few things before you begin the application process. First, unlike wooden panels, vinyl panels are poorly suited for adhesion. You must abrade the panels, using friction-based techniques, or they will eventually shed the new finish. In addition, you must apply a type of paint specifically formulated to bond to vinyl panels and trim, or you will end up with a finish that won't last long.
Open the door and remove the vinyl door panels if possible, using a screwdriver. Leave the coverings in place if you are unable to remove them.
Sand the vinyl panels with 220-grit sandpaper to stimulate adhesion. Scour the panels until they feel slightly rough.
Cover areas of the door you do not want painted with low-tack blue painter's tape. Cover larger portions of the door with plastic coverings. Use painter's tape to stick the plastic coverings to the door. Use scissors to cut the plastic dust sheets into smaller pieces if necessary.
Wipe the abraded door panels down with a tackcloth.
Coat the abraded vinyl door trim with a vinyl trim spray paint, holding the can 8 inches from the panels as you apply. Wait one to three hours for the finished trim to dry. Add another coat if you have poor coverage.
Do not become too aggressive when trying to remove the panels. If you have difficulty removing the panels, simply leave them in place and cover adjacent surfaces with plastic and tape. There are a variety of brands of spray coatings specifically manufactured for vinyl panels and trim. Read the labelling to ensure the brand you choose is formulated to bond to vinyl. You can find vinyl trim paint at automotive accessory stores.
Do not paint over unsanded vinyl door panels, or they will eventually shed the new finish. Don't use an ordinary acrylic latex or enamel paint to coat vinyl door panels, or the finish will eventually fail.