The method you employ to remove scratches from your car after it's been keyed depends on how deep the scratch goes. The first coat on top of your car's steel frame is a primer, which is followed by the actual colour coat and then a clear top coat. If the scratch went into the primer or the steel itself, you'll need to repaint the entire panel. However, if the scratch did not fully penetrate the colour, you may be able to buff the scratch out yourself.
Look into the scratch and check whether you can still see your car's colour. If you see steel, you may have to repaint the entire panel. If you see colour in all or part of the scratch, you can attempt to repair the damage yourself.
Rub a substance of a substantially different colour into the scratch. For example, rub black shoe polish into the scratch if your car is white. This will ensure that you don't sand down too far.
Attach the sandpaper to a sanding block. Dip the sandpaper into a solution of water and three drops of dish detergent.
Sand at a 60-degree angle to the scratch, moving along the length of the scratch. Wet the sandpaper frequently between strokes. Continue until you no longer see the substance -- shoe polish in this case -- that you rubbed into the scratch. Be careful not to sand through the paint colour.
Look at the dishwater: If you see colour, you sanded through the top clearcoat and will need to apply a new layer of clearcoat.
Dry the scratch with a hair dryer, heat gun or out in the open air.
Squeeze rubbing compound on to the scratch. Polish the scratch with a cloth, by hand, or with a polishing wheel. Be careful not to polish through the paint layer.
Wipe away any remaining rubbing compound with a cloth.
Wax your entire car after repairing the scratch, for the best results.