I only strafe Panzer IV's from the high 6, I aim for the engine deck and try and land my hits at less than D500 and pull out before i hit. If I have a Yak9t or Hispanos I will 6em some times from low and close firing into the rear. all u nead to do is smoke the engine or turet, it has been my experance that after this occures you will get the kill on them as they spawn out,if they dont spawn out and hange out you have done so much damage that nomater what anyne else does to them you will most likely get the kill, some times they will even blow up from an outright kill. This can be done with 50cal's although it apears harder to do now that they have fixed the armor leak around the turet.
Strafing the tracks can disable the tank,but this will not get you a kill a quickly, you ammo is better spent on the engine deck.
Osty turets can be taken out by any airborn gun, I prefer a near 90degree drop on to the osty, when i was using the A6M2 to do it I simply waited till the osty was looking the other way then dove directly down on him and put a 1 sec burst of 20mm into the turet top, it would kill the gun he would die spawn, i got the kill. any weapon can do this from my experance, 50KG bombs(or 100pounders) work to you just nead to be accurate.
The 23mm cannon on the Il-2 is probably the best anti GV gun, the the Hispano, then the 37mm yak canon.
Tigers nead bombs, one 500 pounder is enough, prety much have to hit them though.
Their is no real secerat, just get close and dont miss, minamise the angale of atack as much as possable