HO Scale Weathered Freight Cars

First time trying out my new airbrush.  Colors I used were burnt umber, orange umber and dark brown.  Weathering powders were used as well.  Sorry for the poor quality photos.  All my pictures are taken with my droid phone. 

Intermountain Railway Co. 5277 cu. ft. Boxcar.

Walthers BN PS-2 2893 cu. ft Covered Hopper

Walthers GN PS-2 2893 cu. ft Covered Hopper