-The soviets are very good at one thing, at least in a friendly enviroment: stacking bonuses.
If you put a commissar, a commander and a medic not to far away from a crucial squad, you're pretty sure that this particular point of the battlefield is in to stand fast. You can also blob like no tomorrow and have multiple squads beneft from it to form a quite resilient spearhead... Just be careful not to suffer to much from artillery strikes!
-Despite your army rule boosting artillery, take rather an air observer, it can more often than not turn to be a 75pts delete button.
-Look into some mg-fitted armoured car. In bolt action, with anti-tank weapons being relatively limited, and MG pouring way more reliable fire than a single cannon shot, plus the fact that they are way cheaper, makes them very interesting.
-If you field an mg equipped squad, mount them in a truck or play them as scouts to grant them upgraded flanking: either way they'll get more opportunities to close on your opponent.
That's all what comes to my mind. Good luck and much fun in this great game that is bolt action!