Over the weekend, I put the self-made decals for the Whitcomb 50-tonner for the Army markings and builder plates. I decided on very light weathering, but enough to see it's been used in the short time the locomotive would have been on the line. I limited the weathering to what it would look like on any given day before heading back to the Army spur and the first Sergeant having a look at how 'his' engine looks at the end of the duty day.
It's sort of hard to see, but I put a little bit of weathering on each end and along the running years but a little highlights and just a tiny little bit of smudges along a car body and the roof as well as the area of people would be walking into the cab from along the walkway.
Other than that, I think the Army would keep it just about as clean as it appears here, especially if it was brand new not long ago when they got it.
This last shot shows the wear I placed from footprints and grime along the steps and walkways, which would accumulate almost right away...
-Lee
Flickr photo set of my On30 layout