I would say big thing when it comes to rivets in general is don't make them uniform in any way. These are not planes right off the show room floor they are weathered, beaten and generally worn from time and maintenance. I used similar standards when working with paint but also focused on areas that were known to have more wear and tear creating the illusion of chipping paint at walking areas, dirt both in dark and white coloring dependent on the color of paint below and even the theater of operations that particular plane was operating out of during the war. For bare metal good thing to remember is it's not polished metal, it should have evidence of random scratches and dull metal in some areas. I used a cloud effect on one of my layers so it would affect the paint and metal to give that random dulling effect and wear. It's not about perfect lines or rivets and I can tell you that from my years of working in the aviation industry on military aircraft. Position means everything but how they visually appear should not be perfect and uniform. Oil, fuel, hydraulic fluid and many other things will discolor and change the paint overall so take good looks at examples and try to mimic them.
