Thanks James, Erik, Michael, and Greg!
Greg, the brownish tint of the weathering is done by two different techniques. The wash I used, MiG Ammo Deep Gray, has a decidedly brownish tint. I remove it before it completely dries, so it gives it a bit of a brownish stain in some areas as I wipe it off in the airflow direction. But what really gives it some extra pop, with a bit of a brownish cast, is the Tamiya smoke. I spray that over random panels, sections, panel lines (not all, just randomly), and areas where dirt and staining would collect. Heavier in some areas, lighter in others. I also use heavily thinned Tamiya rubber black to simulate soot and other darker dirt areas, such as on the vertical stabilizer right above the horizontal stabilizers.
Hope this helps!
09. May at 23:40:06