Raven,
Couple of things:
The model looks very good as it stands. If you want to recreate a big metal thing with a small plastic thing, you have to cut corners somewhere. You also have to decide what you're trying to recreate (or evoke maybe).
You've got history on your side no matter how deeply you weather a tank. Tanks were produced in the tens of thousands - especially Rooskie tanks - (about 40,000 T-34s?) and loss rates were sky high. So if you want to consider your model as representing a vehicle new to the front, you've got it made and there were dozens each day during the war exactly in that category.
Might add that the most famous tank meister of ten to fifteen years back was Tony Greenland. He only did German AFVs I think. His "look" defined a good model AFV for years - very crisp, tons of drybrushing and even some color contrasts. He did use chalk as a pigment for the very light weathering he did below the hull. He was very restrained using it, saying he was building tanks, not the mud they fought in. Perfectly valid idea. A reaction to the Greenland style came from the "Spanish School" builders who argued the case for heavy weathering. Mig Jimenez and Adam Wilder were pioneers and remain top modelers. Both were affiliated with Vallejo - a Spanish company - and found local gurus there who were keen on bringing the techniques long familiar with artists to the model world and introduced pigments on steroids.
Vallejo remains one of the great art painting companies today. No accident the pigment craze started there. Every paint has a pigment and because many painters still like to make their own paints, artist grade dry pigments are commonly used. You want the finest pigments on the planet? Go to Blick and get dry pigments from the fine American oil paint company Gamblin - about $6 for 4 oz) or the ritzy French Sennelier for $10 for the same. That's a lifetime supply. MIG is the biggest seller with a blizzard of colors - very good - but pricey. And frankly you don't need more than maybe four colors to take you the distance. MicroMark sells Doc O' Brien's "weathering powders" for railroaders - $20 for 12 small bottles which will last a long time. They have an adhesive which allows them to stick on without ISP or mineral spirits. Tamiya makes a series of weathering sets that use the same idea. Each work nicely.
It was the Spanish School that emphasized lots of pigments, chipping, filters and pinwashes. Here they're going for the used look of a combat vehicle. Lately they've drifted into complicated color theories (modulation) and an even greater use of oil paints. These guys have founded companies to push their approach. MIG was the first (Jimenez was involved very early but no more). Now AMMO (which used to be AK Interactive) which is run by Mig Jimenez. Whether the blizzard of materials they push are really needed is something I doubt. (I do know that Abteilung oils are the most expensive oil paints per volume on the planet and I seriously doubt they'd do any better than a "student grade" oil paint from any art shop.)
It's the Spanish School that's accused of over weathering. Often I think that's true. I'm not at all convinced that the complex modulation painting is needed. (I believe both Stik and Bish have expressed similar sentiments.) On the other hand, there were certainly AFVs that fought under very harsh conditions and were lucky enough to stay alive long enough to get properly messed up. And it's fun to do that kind of weathering - it's almost a separate hobby.
In my view a combat vehicle would above all be dirty. I don't care how long they were in the field - tanks throw up lots of dust, dirt mud etc - and will do even more if there are other tanks in front of them. Whether you need buckets of chips and rust is a very different question. So the technique I'd center on would be pigments to use on the wheels/tracks and some kind of dust for the hull.
Resources: Check YouTube. There are megatons of weathering videos there. Search "Mig Jimenez" and you'll get excerpts from many of the DVDs he made covering all kinds of tank weathering. ("AFV Arcylic Weathering Techniques" will bring up a complete DVD and the one I think is the best of the lot - but I like acrylics a lot.) I give the strongest thumbs up to Mike Rinaldi's "Tank Art" volumes (a steal at $25 considering the size and beautiful photos) available at Rinaldstudiopress.com . (Rinaldi has aircraft volumes coming: that I want to see.) You may find Rinaldi complete overkill but the results he gets are impressive whether realistic or not. A review of Tank Art I is on YouTube - it's in German but the guy goes slowly through the book which is in English - quick way to get the idea.
You don't have to go down the whole road. I've learned a lot from Jimenez and company and it has influenced all of my modeling - ships, tanks, planes. But the subject is a bottomless pit.
Happy Thanksgiving
Eric