Sean:

I emailed the pictures to you. The plane was painted with latex exterior flat paint. The gray and black washes were also latex. I mixed a couple drops of paint into lots of water. Basically, the washes were colored water. I used an airbrush to apply them. It took several light coats before you can start to see the effects. On the last plane I did (unfortunately I do not have any pictures) I used artist chalk to get the effects of the black wash. I like the artist chalk better because you have more control on how much you put into a panel or how wide of an oil streak you simulate. If you are applying a clear coat, do not use lighter colored artist chalk to simulate paint fading. The clear coat will turn it dark. I found this out the hard way . The plane that I used artist chalk on crashed and burned but I still have the tail section and wing. I will try to get some pictures of the tail section and wing over the weekend and send them to you so you can see the different effect it produces over airbrushing.