scratches and dings will yield a good result. If your rock guard is in good shape, and by that I mean no significant gouging, scotchbrighting has been used as surface prep. If your bumpers or any surface has already had one repaint, stripping must be done. Paint needs to be thin if it is to be durable. Typical OEM jobs are .003 to .005. 1st job takes you to .008 or thereabouts. Custom color sanded finishes can be .020 or more. These while beautiful, easily chip.