I just fired up my airbrush and did a light coating of grimy black on my SD-7 in CNR fatasy scheme. I airbrushed the trucks, fuel tank and pilots a bit heavier and then lightly sprayed the yellow stipes and Canadian national decals to tone them down a bit. I then sprayed the rad and dynamic brake grills then misted a bit of black acros the top to simulate diesel soot. I'll probably add some more streaking down the fuel tank and pilots as well as a wash over the top fans.