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.

Adding Panel Lines to ACF Hoppers
Bill Mock
January 2010

Here's [ ... ]

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 [ ... ]

I've finally added as much plaster cloth as I expect I'll need, and have moved on to priming the base before painting it.  Priming made it look unfamiliar, [ ... ]