Whether it's graffiti or someone's idea of a "custom" paint job, spray paint can make any car look like the underside of a bridge. The problem with some types of spray paints is they're made of the same stuff as the paint on your car. Fortunately, spray paint goes on thin, meaning that solvents can easily penetrate and break its hold on your car's finish. The trick is to use a short-acting chemical that's aggressive enough to remove the spray paint without damaging the car's original finish.
Park your car in a cool, well-ventilated area out of direct sunlight. Don protective gear and apply some of the paint-removing chemicals to the non-synthetic lint-free cloth. Purchase a commercially available paint remover, or mix a batch of your own. Saturate a small area of the cloth.
Apply the chemically saturated cloth to a small section of the spray painted area and allow it to sit for a minute or so. Depending on the chemical used, you may need to remoisten the area to keep the solvent from fully evaporating. After allowing the chemical to sit for a minute, scrub the paint off with the lint-free rag. Reapply as necessary until you remove the paint from the car's body.
Remove spray paint from vinyl and rubber in the same manner, but feel free to use a more aggressive approach with a washcloth, if you so desire. Do not use petrochemical solvents on rubber; try rubbing alcohol first and pure ethanol or methanol if that doesn't work. Even vodka will do the trick if you let it sit for long enough, it is after all, about 40 percent ethanol by volume. Scrub the area with your washcloth until the paint comes out.
Reach into corners and crevices using a stiff, natural-hair paintbrush. Don't use synthetic bristles, or the solvent will eat them. Boar-hair brushes are ideal for the deep recesses around windows and rubber trim, but may scratch paint. Use a pair of brushes, one to apply the chemical and another "dry" one to scrub it away. Keep a towel on hand to wick solvent away from the "dry" brush.
Wash the entire car and allow it to air dry. Check for hazing in the paint where you removed the spray paint. If you see any, allow the paint to sit untouched for a week so the topcoat has a chance to re-harden fully. The hazing may be a result of chemicals in the spray paint leaching into the car's clear coat and causing it to soften; if you polish it now, you risk destroying what's left of the topcoat.
Hand polish the car using a commercially available polish. Use the finest grade available and be patient. The topcoat may not have completely hardened even after a week, and using an aggressive polish or buffing machine can strip it away. After polishing, wash the car again to check for any hazing you might have missed.
