
Reposted from the comments section:
Here's the process I used on the Trukk:
Everything metal(even if eventually painted red) is based with Tin Bitz.
Any areas that will be painted red are painted with Mechrite Red. This is followed by a heavy drybrush of Blood Red.
Next, Iyanden Darksun for anything Yellow.
Now, it's time for the Boltgun Metal. Get your nasty brush out. Drybrush heavy on the Tin-Bitz areas, and lightly on the red and yellow areas.
Give the entire thing a heavy Devlan Mud wash.
Basecoat the actual rubber tire areas with Charadon Granite, follow with a Badab Black wash.
Last step is to take whatever color your "dirt" is and drybrush that over the tires, along the front, bottom and back of the trukk. My "dirt" color was Solar Macharius Orange, as I'm basing my Orks on a Mars-ish landscape


Now these Tau models I had painted some time ago. I'm re-showing them because I experimented with re-basing them:

