The first thing I typically do after the entire tank is together - tracks and everything - is prime the whole thing with flat black (tTamiya acrylic). Once the entire tank is black, I go over that with a very light coat of the main color, allowing the black to show through (or at least darken the base color), in this case Tamiya dark yellow. I keep adding light coats of the base vehicle color, mainly towards the center of panels etc. In this case I left the suspension a darker shade of the base than the upper parts of the vehicle.
I guess most people gloss coat their models before applying a wash, but I don't. I mix a VERY thin potion of oil paint thinner and burnt siena (in this case), and apply this over the whole vehicle. It goes on heavier on the suspension parts. In order to get the different shades, I mix up different washes, all with subtle differences in shades. From essentially black - to light tan. I just kept going over the running gear with various washes until I was happy with the color. Make sure you let each wash dry before you apply the next one - otherwise it is hard to tell what the final outcome will be. The tank looks different when the oil paints are wet. In order to get a proper perspective as to what your wash did - you need to let it dry. At any one time I probably have 6 or 8 washes in jars - ready to go - depending on what I think the tank needs.
After all of the washes are done - I gloss coat, decal, flat coat, then use pastels to get that "final" dirty appearance. I generally don't do any dry brushing - if I do, I dry brush tools and accessories - not the whole tank.
All of the different colorations were done with pastels - The only colors I sprayed on the StuH with the airbrush were the flat black primer, and Tamiya dark yellow.
I'm glad you like it - I'm pretty pleased with the results. This was the first model I completed using pastels - so I was kinda experimenting along the way.
Jeff
Bye the way - I never even thought about the cable in the tracks

You're right - that's asking for trouble. Funny what one person notices that the other doesn't .