For early T-34's you would want to use Humbroul 114. It is russian green. if you have it, knock yourself out. if you dont... I'm not sure where you can get it (sorrey).
For late T-34's and IS-2's etc I followed Cookie seewell article at FSM. He suggests to use RLM 80 (Maybe I'm wrong? I dont remmember exactly right now, but I'll check it out) Schwarzgrun - Black green. However I used it only as a base coat and highlighted it more with a lighter green.
I hope I will be able to show pictures of my latest IS-2.
I'm sure the gang here will also provide you with good info.