I have a friend who found a '62 VW single cab. It has a nice patina of dove blue that is sun baked; primer, and bare metal showing through. Only problem was, someone had replaced both doors that were red and white two-tone. We stripped the doors of all paint and used a gray etch primer; covered that with another two-part gray fill primer. The we had a paint shop mix us a quart of paint matched to the burnt out dove blue so we could get the hues in the right shade. Then I just went to town with the sand paper and went thoguh the paint and into the primer. Sometimes even through the primer to bare metal. I kept the sanding along edges that would naturally wear and where sun would fade the paint. Afterwards, the owner had a sign painter do some logos and faded those as well. The overall effect was perfect.