An easy way to enhance the look of any diesel locomotive is to blacken the grills and vents to provide more depth.  You can use a black wash to bring out the grill or vent details.  Weathering powders are extremely effective bringing out locomotive vent and grill details.

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 [ ... ]

     Since NOBODY will be reading this I guess I can vent here. 

     Same thing other people have griped about in [ ... ]

I've read lots of advice, howto, intro, and helpful things on the internet about modeling railroads.

But nowhere is there any information for the beginner, [ ... ]