I decided to try and weather my Lionel L1 Pennsylvania locomotive. This was one that had the wrong shade of green. I don't have an airbrush, so this was done in the "dry" brush method. I had some previous experience with weathering a water tower, and a fire lookout tower for my layout.
I used Badger "Weathered Black" to apply the first coat all over the locomotive. I used Model Power "Chocolate Brown" to apply the dirt color around the bottom part of the engine. This is supposed to represent dirt rather than rust. The tiniest amount of white to represent water/mineral deposits around valves and such. It's basically complete. I just need to touch up around the cab and such, then apply a coat of dullcote to protect it.
I used several color photos of actual L1s as references.
I think it turned out better than expected. I probably won't do another engine, at least for a while.