If you would like to paint a motorcycle helmet yourself, you will have to factor in a couple of considerations. First, because motorcycle helmets are made of fibreglass or acrylonitrile butadiene styrene plastic, they aren't especially conducive to paint adhesion. Second, because the helmets are slick and nonporous, it can be difficult to generate a smooth, professional looking finish unless you know the proper application techniques.
Detach any parts of the helmet that may interfere with your ability to paint using a screwdriver.
Clean the surface of the helmet using soap and a coarse brush. Rinse the soap away using a damp rag.
Allow the helmet to dry completely.
Abrade the surface of the helmet to promote paint adhesion by sanding it with 400-grit sandpaper. Do not over-sand. Stop sanding when the surface of the helmet feels slightly rough to your fingertips.
Wipe down the motorcycle helmet with a tack cloth.
Lay the helmet on top of a fabric dust sheet. Cover any areas of the helmet you want to protect from paint over-spray with painter's tape.
Apply a very light coat of spray primer. Apply in very brief, intermittent bursts rather than in a long, constant flow or you may end up with runs or drips.
Allow the primer to dry for three full hours, and then apply acrylic spray paint in the same manner as you did the primer in step seven. Do not try to cover the helmet in one coat. Apply only a light coat to encourage a smooth, professional looking finish.
Allow the paint to dry for two hours, and then apply an additional coat if you can see the primer bleeding through.
If you want to add logos or designs to the motorcycle helmet, use decals instead of paint or you are likely to be disappointed with the final results.
Never attempt to paint a motorcycle helmet without abrading the surface with sandpaper, first, or the paint will not stick. Never attempt to paint a motorcycle helmet without applying a coat of base primer or the paint will peel up over time.