So ords are down, VH is down and enemy tanks are rolling towards your field? Do not despair, as there are still two tools in your box that can effectively thwart any GV attack: The Il-2 and the Hurricane IID.
What does NOT work:Strafing tanks with MG armed planes.
What does hardly ever work: Strafing tanks with ordinary fighter cannons. While you might occasionally track a tank with huge amounts of well placed heavy gun hits, it's usually not a viable way to stop any GV. If you get the kill, it's in 99% of all cases because someone with appropriate weapons killed that tank, and you just get the credit.
(However, both MG and cannon armed fighters are fine for disposing light armoured vehicles and Ostwind flak panzers)
And please take note that the 37mm cannon of the Yak-9T is not suited to tankbusting, it is firing HE rounds.
What does work: That being said, let's now look at our tankbusters of choice:
The Il-2 is good for attacking: All light vehicles (M3, LVT's, M8, Jeep, M16), Ostwind and Panzer. With a bit more effort you can learn to destroy the Sherman Firefly. T34s are very hard to stop, the Tiger is impervious to the 23mm rounds.
The Hurricane IID is good for attacking:Actually there is no vehicle in game which cannot be busted by the Hurri's 40mm cannons. But the slow rate of fire and few ammo makes hitting and killing small moving vehicles like M3's, M8's or Jeeps quite difficult. And the Hurricanes slow speed, low volume of fire and fragility makes attacking Ostwinds a sucidal undertaking, even M16 are very dangerous. Leave those two vehicles to the Il-2 or fighters.
Panzer, Sherman and LVTs are easy meat. Both T34 and Tigers are difficult targets, but far from being invulnerable.
How to do it:Don't take much fuel. If you are defending your own base, you don't need much cruising time, and you want your plane to be as light as possible (climb rate & maneuverability). Usually 50% (or 25% in case of the Il-2) will do, though you might want to give the Hurricane 75% to give it a flight time of about 18mins.
Set your cannons convergence to close / mid range, as you want to both cannons to hit the target and that at a close range as possible. I have set the Hurri convergence to 300 and the Il-2 convergence to 250. It's not more effective to set the convergence much closer though: The steep angle required to kill M4' or Tigers makes shooting at distances under 200 yards hazardous.
Climb to 2000-3000 feet to get a overview and to spot the targets. While you are scanning the ground, don't forget to watch the airspace for enemy fighters. Ground attackers do suffer a lot from target fixation. If your base still has radar, do a quick glance at the map to spot any inbound air cons before they suddenly appear behind your six.
When finally attacking, do only shoot with your cannons.Your light machineguns don't add any damaging capability and just clutter up your view. Exception: When attacking Ostwinds, the increased volume of fire will greatly help to take out the turret (see below).
Basically, there are two ways to attack your prey:A) A low run on the deck, pumping your rounds at close range (D200) into your targets rear end while flying level or in a very shallow dive.
Works fine against all unarmored and armored vehicles up to Panzer / Ostwind. This is the same tactic that was used in the real world, but fails to have any impression on T34 and Tiger, and most of the time even on M4.
B) A dive onto your target, so you you pierce the top armor at a steep angle.
This is the required method to kill M4s (with Il-2 and Hurri 2D) and T34/Tiger (with HurriIID). It's also the best method to attack Ostwinds in an Il-2 because of it's open topped turret.
Try to approach your target from it's six oclock, especially when it's still moving. Look for a egress route when setting up your attack, you don't want to crash into trees or buildings, so adjust your attack approach accordingly.
When nosing over, reduce your throttle to about 1/4th. Speed kills, because it just makes pulling up early enough more diffcult. The faster you dive, the less firing time you have, too.
Like mentioned earlier, use your cannons only. As we have icons, ranging shots with MGs are not necessary. With the Hurrican IID, use single short or very short burst in case you are absolutely sure to hit, as your ammo is very limited and you don't want to waste even a few rounds. Flying the Sturmovik, you can and have to be more generous.
Aim for the turret top or the rear hull top (engine compartment). The latter is the place you absolutely want to hit a Sherman when you are flying the Il-2, as the M4 has thicker armor on its turret top. The steeper your dive angle is, the easier it is to pierce the armor. While for Panzers and M4s 30-45 degrees are usually sufficient, you will need to dive even steeper to bust T34s and Tigers. But be careful, steeper angle = huge risk of augering!
Similar to buff busting, set up your attacks properly and with patience. If you see your attack run won't probably work because your enemy starts to evade or there is an increased risk of augering because of a botched approach, just break and get around for another approach. And don't forget your cursory glance for enemy fighters!
Appendix:1.5MB Zip file containing three small Hurricane IID films: Two M4s 4'25"
One M4, one Panzer 1'42" (Originally part of a longer sortie resulting in 5 kills.)
One Tiger 2'49"
This picture illustrates the best point to aim at when attacking a Sherman Firefly:
edit: fixed the download link