Mi Amigo !
If your Client says he will be happy to see it touched up, then I would try my old standby - DrColorchip..
Have used it many times and it is always predictable..
If you can very carefully fill in just the scratched areas, let it dry the allotted time, and then go over it with the other product to remove any paint not in the scratch, it will certainly fill it in..
You want the scratched, filled, surfaces to be perfectly flat with the rest of the paintwork, and that alone will have to be better..
Examine all around the damaged areas before, and see if there is any surface scratches, etc., that can be carefully removed Before you begin the fill in process, so you dont have to try to remove them after its painted..
Or, you can fill it all in, let it dry at least overnight, and very lightly sand flat all around it with a 3000grit piece of wet or dry, and then very carefully compound the area and polish it up..
Do you have something you can practice on first before you go do this?
It is very tedious work if you want to do this correctly..
I use a camels hair sword brush(from when I was Painting) that they sell at most Auto Body/Paint Supply Shops.. When its wet with a little solvent/paint mixture, it comes to a very very fine tip that allows you to just touch inside the damaged area and leave a line of paint..
The Dr Colorchip kit will give you some brushes of different sizes that will also work..
Think about this, see if you can get something to try it out on if possible, and now you have another option !

Good Luck !
Dan F