A quick and simple method to get rid of the plastic new freight car look is to spray a light coat of Dullcoat.  This will take away the 'toy' train look of your layout.  If you don't have any Testor's Dullcoat you can use any Matte Finish spray to get the same results.  Just a simple spray to each side and let dry.  This can be done to any plastic kits also.

Hopper Weathering Clinic III
By Bill Mock
January 2010

OK, I gave the inside of these hoppers a wash of Engine Black below the coal line. They [ ... ]

This is a test of some photos I took with my iPad2. It's all z-scale stuff - code 40 ME unweathered rail with z- and n-scale PCB ties from handlaidtrack.com. [ ... ]

 This is Micro trains Line SD40-2 Santa Fe model which I customized with working ditch lights.