French modeller has weathered with perfection this nice model, see here:
http://us.leforum.eu/t4980-ON30-280-BACHMANN-WEATHERED.htm
Very nice! I did a google translation, and came up with flat polly scale, I think it was air brushed, similar to a method he described for his Davenport. It looks like a painstaking process:
http://us.leforum.eu/t651-ON30-040-GAS-MECHANICAL.htm
Mark
A well used not so maintained appearance. Looks like the look he wanted was well achieved. My loco shop engine wiper employees better keep the maintenance up or else!!! :D