Tips for painting plastic include using liquid sander instead of sandpaper to provide a clean surface for new paint and choosing paints formulated for use on plastic, like Krylon Fusion for Plastic, Rust-Oleum Specialty Paint for Plastic Spray or Valspar Plastic Spray Paint. If spray paint not formulated for use on plastic is used, the surface should be primed with a product like Rust-Oleum's Specialty Plastic Primer Spray. Painting smaller projects may be easier with a paintbrush than spray paint.
To paint plastic, first wash the item to be painted with water and dish soap to remove any debris or grease. Rinse thoroughly, and dry fully. Apply rubbing alcohol to the item, and let it air dry.
Move to a well-ventilated area, and cover the surface with a drop cloth. Place the item to be painted in the middle of the cloth, and carefully use sandpaper to take any shiny paint off of the item without leaving scratches on the surface. Remove any dust with a cloth.
Use painters tape to cover any part of the item that will not be painted. Shake the can of paint, and spray a thin layer of paint over the object. Wait several minutes for the first layer to dry before adding a second. Continue spraying until the desired color is achieved, and let the paint dry before using the item.