Write an article based on this "Wash the plastic object with soap and water. Sand the surface with a 220-grit sanding block. Apply a coat of primer to help the paint stick. Spray a coat of black spray paint on the plastic. Protect the newly-applied paint with a clear primer."
The paint will stick best to a smooth, dirt-free surface. Dip a washcloth in soap and warm water and clean any dust or debris from the plastic's surface.  For a thorough cleaning or to remove stubborn dirt, immerse the object in water instead.  Dry the object off with a cloth before painting it. Sanding provides texture to help the paint stick. Rub the fine-grit sanding block with firm pressure over the plastic's surface. When you're finished sanding, wipe away any dust with a dry brush. If you don't have a dry brush, a paint brush works as an alternative. Spray a coat of paint primer over the object's surface. Avoid spraying one area for too long to keep the coat even and light. Let the primer dry for the time recommended on the packaging, which should be between 30 minutes to an hour.  You can buy plastic primer online or from most craft stores. Thin primer coats are ideal because heavy or multiple coats can change the object's texture. Hold the nozzle about 12–18 inches (30–46 cm) away from the surface and move the can in smooth strokes over the object. Continue spraying the paint in overlapping strokes until you cover the entire surface.  Apply 3-4 coats to strengthen the paint's color, waiting for it to dry in-between coats. Each coat should take about 30-60 minutes to dry—check the paint's packaging for a specific time. After the last paint coat dries, spray the entire surface with a clear paint primer. This will prevent the paint from fading, discoloring, or chipping over time. Paint primer is especially important if you will use your object outside, where it will be subject to the elements.