You'll also want to be able to punch back and take any spots that are next to Russia, so picking up Artillery to match with your infantry is a must(IE Build should be 4 inf 4 art in Russia pretty much every turn). So you don't need mobility, but you need people, so Infantry are great. In order to do that you need to be sure that Germany can't hold a territory next to Russia.
In order to do that, you need to keep them out of Russia. Generally the strategy is Russia just needs to survive, and let the UK/US do real damage to Germany. Note: I haven't played 1942 Second Edition, this is based off of plays from AA50, 1942 1st ed and the original.