Hugh,
I've got airbrushes too.
The factory finish is so superior to aftermarket paints it is scarey.
First of all on my 2000, the clear coat is actually soft! You can easily mark it by pressing your fingernail into it!
Sounds terrible, doesn't it!
Actually not, first, it is much harder to chip, and second, the chip does not leave a "white" fracture surface. In otherwords, this clearcoat behaves as if it were "wet."
This is not a polyurethan clear that DuPont etc., sell.
Fixing the scrath is related to fixing a scratch on a camera lens. The first rule is do not make the scratch/defect any bigger. And second is make the scratch black so that light will not reflect on the crack facets. Related to this is a poorly fitted hood on a Viper. If the car is black, you "can't" see the gap. If it is red, white, etc., the gap really stands out.
Seriously, if you fill the scratch with a 4 hair brush with magnification, you can build up paint layers without touching the paint next to the scratch.
While the airbrush will make a small repair area, even if you spray thru a template you are going to now have a repair area (length times with) that is 10 to 100 times as big as the scratch.
I believe the repaired area will not age like the original paint and that even if a "perfect" repair can be made, it will not be stable in time. So my conclusion is, keep the repair area the size of the scratch itself. (NOTE: If you are able to fill the scratch with basecoat if required and then clear coat, then, it would be OK to block the clearcoat of the scratch an adjoining original clearcoat to obtain a smooth surface. The "block" would be something like 1/4" by 1/4" in area and done most carefully with magnification.)
Naturally, I'm splitting hairs and that an airbrush repair may be acceptable.
...and yes, if I was not going to "fill" the crack, I would definitely use one of my airbrushes.
However, I would NEVER consider using full-scale body shop equipment. That is for repainting a major repair or panel replacement.
...and I admit, there may be some ultra high-tech scratch technology that is quite different from conventional autobody - sort of like how they "fix" stone cracks in windshields. If such techniques exist, I am unfamiliar with them.
Good luck,
Tom
PS. A friend of mine bot a new Dodge pickup and the next day backed his van into it making about a 6" dent. He had it "fixed" by a locally good body shop (it was a NEW vehicle and he wanted it like new). Needless to say, getting it "fixed" was worse than just leaving it alone.