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
By Bill Mock
December 2009

Here is the first stages of weathering of my new BN [ ... ]

So there I was..had my speeder all painted and glass in the window and everything dull coated and figure inside and..hunky-dory.
I went to LHS becasue [ ... ]

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, [ ... ]