Vinyl surfaces must be prepped before you paint them. Vinyl is often slick, and even when a vinyl surface is textured, the textured surface is still nonporous. These conditions don't give standard paint much to adhere to. The best way to prepare vinyl for painting is with some light surface abrasion, cleansing and the right kind of primer. If you prep the vinyl surface well, your fresh paint will apply just as it would to a normal drywall or wooden surface.
Things You'll Need
Airless spray gun
Wipe down the vinyl with trisodium phosphate and a sponge. Certain cleansers can damage vinyl surfaces, but trisodium phosphate cleans safely and doesn't leave behind residues that could react with paint.
Sand solid vinyl surfaces with 220-grit sandpaper for light surface abrasion. Vinyl items are not always made with 100-percent solid vinyl. What you think is pure vinyl may actually be medium-density fiberboard or a similar material covered with a thin vinyl coating. If you are not sure that your vinyl is solid, do not sand it; you don't want to risk sanding off the thin vinyl veneer. When you abrade a surface or apply specialized primer, the surface accepts paint easier. Either method allows for good adhesion by itself, and using both in combination is a smart bet for the absolute best results. If you're unable to sand a veneer surface, you can still proceed with paint and primer.
Stick painter's tape to any areas that you don't want painted. Protective taping is vital to prepping any surface, because even experienced painters make mistakes.
Prime the vinyl surface with bonding primer using a paintbrush, roller or airless spray gun. Bonding primer is formulated for better adhesion to nonporous and slick surfaces, like vinyl or glass. Wait for the primer to dry. Bonding primer takes longer to dry than general purpose primer, so consult the container's label for the manufacturer's recommended drying time. Once the primer is dry, the vinyl surface is fully prepped for painting.