First item of discussion, tamiya plastic cement. This is liquid wonder for constructing anything made from polystyrene. It is very thin and holds very strong. The small brush included with the bottle really helps getting cement in those tight spaces. The cost: $5
The next items are the weathering masters. I use series 1 and series 2 almost exclusively. As shown, the first one comes in sand, light sand and mud and the second one comes in snow, soot and rust. There basically made from ground pigment. They can be applied using the feather brush to make a dusty look, the foam applicator to make smears or a damp paintbrush to make stains. The cost: $11
The last product I will discuss, which really makes this project, well, not shine is the weathering sticks. These babies set my back about $6 each stick, but are well worth the investment. From what I can tell, there made of basically ground pigment the is moist. It has a texture like damp clay. There is basically two ways to apply it, smearing and dabbing. Smearing makes it look like mud that hasn't stuck to the vehicle, and makes a smooth finish. When dabbing, it makes nice chunks of pigment that really looks like built up mud around the tracks. Be warned tho, dabbing uses the stick at an alarming rate.
Now to the results!