For me, I either love or hate fauxtina and there's one thing that separates the two for me: whether or not I can tell at first glance that it is faked. That's just personal preference of course. The two most obvious giveaways that it's faked are when the paint layer colors showing through are not factory correct, or when the spots showing through the top layer of paint are really blotchy and in areas that would never really have natural patina (like a random spot in the middle of the door). I would study the typical wear patterns on naturally patina'd trucks and try to match the ones you like most as closely as possible.
The bed on my truck is fauxtina, but I tried to mimic original patina on the cab as much as possible. That meant using black sealer/primer and single stage color like the factory paint. Then I slowly sanded through the paint in typical wear areas until the primer started showing through as much as I thought looked natural. I started with 400 grit and worked down to 2000 wet. Then I used 000 steel wool to give it a slight sheen to match the look of the original paint on the cab.
