Here is the Chessie System 4 bay centerflow hopper. Studying from images around the net I found inspiration to this...
The original model, shiny and unused.
First I rubbed down the letters and labels to look faded from the elements of nature.
Then followed some washes , a mat varnish, rusting with artists oils in various shades and mat varnish again.
All graffiti on this one is custom paint. No Decals.