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.

Well here goes nothing. I bought a MTL F-7  trainset, a GP-35 trainset, also a Marklin 81466  Micado steam loco set.I also got 2 packs flex track [ ... ]

Micro-Trains Military Barracks Build by Modelersguild.com

Building this Z-Scale kit was a real pleasure. The parts fit nicely, the materials were right, [ ... ]

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