Wow, you might have more of a problem with the owner than you do with his bloody paint! Yes, key marks
can be eliminated at best or at least vastly improved on depending on a few things:
1) Colour
2) Location
3) Surrounding area paint thickness
4) Time available to do the job
Just to give you an idea of what I do and how I do them, here are a couple of threads where I have done key repairs, one of which was made a "sticky" at AG:
Key Repair-Step by Step Procedure
Here`s one where a guy drove his Q7 from Chicago (5 hours away) to see me b/c everyone in his area told him it couldn`t be done and he didn`t want 1/2 of his new vehicle painted (can`t blame him-everyone would think it was hit by a train, LOL):
Key Repair + Fellow AutoGeek = Huge Pressure
Here`s an example where the very light colour made it hard to make the scratch disappear as much as I would have liked. The customer was happy, but I had hoped for a better result:
2007 Avalanche: keyed twice and faded trim
So, as I have hopefully pointed out, some results are better than others. Let`s discuss the variables I mentioned (colour, location, surrounding area and time).
Colour: Solid colours will offer the best chance for the touch up to "blend in". Metallics are the hardest as they are shot so uniformly out of a paint gun at the factory, that when in a bottle of touch up paint, you`ll be very hard pressed to get the same saturation level of the metallic content as what`s on the paint. Lighter colours are harder to match than darker colours.
Location: To do the very best job, you need to wet sand. This was something I was trained in probably 15 years ago by a restoration shop. I see Mike Phillips has introduced a thread asking people whether they`d like to learn it with an overwhelming number of positive responses. Wet sanding is a double edged sword: It can be a great tool or a great weapon of destruction...depends on how it`s used. Back to location. The paint is always thinnest at the edges and when crossing body lines so to try to wet sand in those locations is almost a guarantee of striking through the clear which then dictates a trip to the body shop.
Surrounding Area: Let`s say you`ve got a key scratch right in the middle of a panel (which looks like what you`ve got for the most part). Green light, right? Not necessarily. If you`re going to wet sand and don`t own a paint thickness gauge, once again you`ve almost guaranteed yourself a trip to the body shop. It`s like playing Russian Roulette. If you don`t have enough clear/paint in the surrounding area, DO NOT EVEN PASS GO...he must go to a body shop. Know your limitations, respect them and live within them.
Time available: The touch up paint needs
at least 12 hours to cure before you should start wet sanding. If he`s putting time constraints on you, he needs to piss off. It takes the time it takes. Period. Don`t have the time? Go to a body shop. That`s non-negotiable.
As far as practical pointers on how to do it, refer to the first link I provided. I tried to make it a step by step guide. I will offer this last bit of advice to you. This is more big leagues detailing. If you don`t have the tools, confidence or ability to try this job: don`t do it. Even if you do, I STRONGLY suggest you get a waiver from him in writing excusing you of any liability if it still ends up needing to go to the paint shop. He`ll still owe you $ for your time trying to help him, so it`ll cost him even more in the long run.
Hope that helps.
Rich
...and thanks Dan for the shout out.