I first started by airbrushing in the Badger Airbrush "Cracked Soil. I did it around all the drains, manhole covers, and craters.
I then worked into the craters some darker brown. I used the Badger Muddy Brown to do that. Finally I pulled in the black color in the center of the craters and I covered all of the metal work.
Next step is to paint all the metal work silver then wash it with an armor wash. I'll then be on to the stuff I don't have any experience on... masking fluid to break up the yellow painted street markings! After that I'll work on oil washes and weathering powders.