Now that I had my buildings put together (Including a card building), I glued them and the craters down to the base and added some rubble (made from cardboard) to the base as well.
One thing I haven't mentioned yet is the ruined gas station. You can see it in the lower left corner in the top picture and then again on the left on the bottom picture. It doesn't look like much from both of these angles, but what it is supposed to be is a small building housing the cashier, with fuel pumps on both sides covered by a large roof. Since this is a ruined city, the large roof has partially collapsed, destroying one fuel pump. I'll have to get some better pictures so you can see what I mean.
I decided to use sand to cover the base and represent both dirt and grass (by how I paint it). The parking lot under the gas station and beside the card building were left bare to represent pavement.
The next step is to prime with latex house paint and then do all the detail painting and washes.
Once I had primed it with gray paint it was time for detail painting. I used Apple Barrel acrylics: Leaf Green for the grass, Nutmeg Brown and Flat Black for the craters, Cobalt Blue for the gas station (you can barely see it under the rain-roof), and Pewter Gray for the roofs. The red was Ral Partha Paints Red.
I pretty satisfied how the sections are turning out. Next one will be primed with spray paint instead of light gray house-paint. Probably dark brown to match my current table.