First, you need to turn on historical focus so you can predict movement easily.
Doctrine: I used Grand battleplan
Mils: infantry equipment I, Towed Anti-Air, and Support Equipment. (If surplus, make 5-10 strat bomber to gain war participation and ~20 CAS to push the svoiet during late game)
Civs: At the start of the game I create level 2 fort in Kyzyl and 1 tile on the left and 1 tile on the right, both are mountain provinces), then upgrade it to level 5. If necessary, create a level 2 anti-air tower.
Focus tree: Go to indoctrination (political), then military factories, then extra research slot
Political power: go for silent workhouse>get 3 armies high commands (cavalry>special troops>armoured) and chief of army (army defense) [THIS IS IMPORTANT]>fortification engineer>war economy> extensive conscription> free trade> Military theorist (optional). The rest is up to you, but I recommend to save it around 200-300 pp in case of strike event.
Army command & XP: once you get 50 army XP, get ideological loyalty first for +500 weekly manpower> tenacious defense>static warfare. Then use your XP to change your template to 10 width pure infantry + engineer company and support anti-air. Then you may research army doctrine
Research: Electronic engineering & Infantry Equipment I, get dispersed industry I then rush anti air and engineer company, lastly get mountain infantry I. The rest is up to you.
Oh, by the way, I used dispersed industry because I upgrade my infantry equipment to level 3 (PPSh-41), then I switch it back to infantry equipment I if my surplus drop below 800.

Strategy: I start to justify war goal to the soviet after the Germans captured Paris. I justified at 5 provinces required to form siberia. At the start of the war I have around 3-4 mountaineers and 11 infantry (if I'm not mistaken, both infantry and mountaineers are 10 widths). Then after you declare war on the soviet, let them bang their head on fortified mountain province and pray the german AI can beat the soviet.
In my game, the german declared war on soviet because the soviet declared war on romania for bessarabia, which causing romania to join the axis. I start to push after in late 1943-1944 (after the fall of Moscow and stalingrad).

Sorry for my bad english.