Apply alloy wheel touch-up paint by sanding the damaged wheel, applying filler if necessary and then painting. Use painter's tape to mask the wheel, and replace it between each step. Use an air compressor to keep the area free of dust from sanding.
Nearly all alloy wheels have a top coat of paint covered with clearcoat. Before beginning the touch-up job, clean the wheel thoroughly. Wash it with soap and water, and then scrub it with lacquer thinner to remove any grease or road tar. Use rubbing compound to remove any built-up brake dust on the wheel.
Mask the area around the damage to prevent scratches before sanding or filing the high spots away. Use 150-grit sandpaper or a fine file to remove the raised aluminum, but avoid making the damaged area any larger.
Use solvent-based filler for filling the indent left by the damage. Once it dries, sand to shape it so that it matches the rest of the rim. If necessary, apply additional coats of filler to account for shrinkage as it dries.
Remove the masking material, and blow away any dust. Remask the area, and apply two coats of sandable primer. Sand the primer, and remove the dust before applying the top coat of wheel paint.