Clean the shower thoroughly using a degreasing compound such as trisodium phosphate. Mix one part TSP into 10 parts water. Dip a scrub brush into the solution and scrub the vinyl, removing any dirt, mold and grease that is on the surface. Wear gloves to protect your hands from skin irritation and open the bathroom windows for ventilation.
Dry the shower surface with clean towels.
Cover anything you don't want to get paint on. Fixtures, shower heads and non-vinyl surfaces can be covered with butcher paper wrapped around and secured with painters tape.
Score the vinyl lightly with fine-grit sandpaper if it has been painted before. This provides a better adhesive surface for the paint. Wipe the surface down with a damp towel to remove any dust created from sanding.
Shake the can well according to the manufacturer's instructions. Apply a think coat of paint on the vinyl, holding the can 8 to 12 inches from the surface. Move the can in a slow, consistent fashion horizontally along the vinyl shower.
Allow the paint to dry for 15 minutes and apply a second coat. Allow the paint to dry for at least one hour before using the shower.