A couple months I was in a very high end shop and they were just putting the finishing touches on a high end resto-mod 67 hemi GTX. The thing was gorgeous and flawless but being a resto-mod they didn't modify much of the sheet metal so the firewall, although cleaned up somewhat, still had the factory ripples etc. But what they did do to minimize the impact was shoot the entire engine compartment and underside with a flattened clearcoat. Taking some of the gloss away really made a difference.