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 [ ... ]

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, [ ... ]