Unless I'm very mistaken, I'd have tought that the conditions and ferocity of the combats in Eastern Europe would also mean that very few tanks, if any (!?), would have made the various battles from the Russian homeland to Berlin in any one piece! Certainly, various bits of equipment got torn away, fenders got bent, petrol tanks got hammered, paint jobs got nasty looking, but major hull warpage would have been only achieved through being hit by ennemy fire or through any other major accident.
So my advice would be: bend the mudguards, remove a wheel and its axis, damage the rubber part of the wheels, give the headlights and the petrol tanks a good beating but unless you are modeling a catastrophic failure, do not overdo the damage and do no bend/warp any structural parts of the vehicle.
Now there are various ways to do this damage. The 'heating' system can work well but can easily be overdone and that will look like what it is: molted plastic... Heat up, over a candle light , some metal contraption (screwdriver?) and bring the heated part close to the model, for instance under the fenders, and let the heat do its trick. You may want to push the heated metal bit into the plastic for more angular looking damage... Another way to do this kind of damage is to bend the plastic cold, with tweezers, plyers or else. Be gentle, or bits might break apart. Rusty bits and holes in thin metal can be replicated with a mini-drill and some careful grinding of those parts. Also, try replacing the kit fenders with some thin soft metal sheet, and bend them with plyers. Does this help?