I've been following military modelers and car modelers to learn some of the techniques they use that might be helpful. One technique I have found useful and I would offer for rusty rivets is to put a few drops of paint on a piece of styrene and use the end of a toothpick to apply paint to each rivet. This is much easier than using a fine brush or dry brushing. I have been surprised at how much more control I have for applying small dots of paint. FWIW
