they dont do the edges (place i went to anyway) they just cover the whole front of the alloy. so i assume it dosent matter how many scratches.
if its not too bad a scratch, try model airplane paint.
i managed to touch the ground with the top of my alloy after a silly handbrake turn.
it scraped fairly badly so i just sanded it down with wet and dry then touched it up with airplane paint. you cant notice it now unless u study the wheel.
might not be as good for the face of a wheel, just a suggestion. I was given this idea by a prof sprayer.