Actually, my method is fairly similar to the one linkws above, though I used gatorboard so the cracks are really defined. Hindsight, I would probably use MDF since I didn't realize you can get such good results with carving. As for the painting, I coated the entire road in Woodland Scenics Asphalt, which is a great black/grey color, and then simply drushbrush khaki. That's it. Thanks for all the compliments.
Joey
P.S. The crater is from GW. I just a cut rough chunk out of the gatorboard to match the shape of the crater, inset it, then covered the holes with compound.