You just have to know how to do it right.
Take no fancy thoughts about precision bomb drops or perfect rocket hits. Think in a crude way. Hit percentages are a petty thing, as long as you are sure you can get the job done.
You are in a plane. You can rearm and reup your plane more than seven, eight times by the time a tank makes his way to the field from a spawn point.
What does that suggest?
Use everything you have, to kill a single tank - make sure you get the job done whatever the cost. And then, if your ammo and ordnance is gone, you can always go and rearm or reup an IL-2.
About 10% of my kills every tour is the Panzer IV, and all of those kills are scored in IL-2s. With each IL-2 sortie, I kill about average two~three tanks, and have killed up to six Panzers in a single sortie w/o rearm.
Typically, the attack sequence in IL-2 starts with bombs, then rockets, and then strafing.
In boming, what one must practice is low alt level-bombing, or low-alt shallow angle bombing against GVs. Pack the 6-bomb package, go up to about 1500~2000ft alt, and start dropping those 6 bombs in a consecutive line, so when it hits the ground, a long 'strip' of craters are made. You get the picture - fly over a tank and lay down the crater carpet above him.
....
The RS-182 rockets are superbly powerful rockets, which knocks out light GVs with just a near hit, and kills tanks with direct hits. Practice low-angle rocket aiming a bit. Find your target, and fly around and approach from the rear. Fire everything you've got against his hind quarters - remember, no sense ruining the whole attack by trying to save a few rockets. Just pour everthing you have. You can always rearm. A direct hit kills even a Tiger, and a near miss usually disables even a Panzer.
Another good method is diving down steeply and pouring rockets on the top-side armour of tanks, which has high probability of killing a tank, but takes some time to do.
....
Strafing, is useless against front-armour. Your targets are tracks on the side, and the rear quarters. Side attacks can knock out a track pretty easily, and rear attacks kill Panzer engines pretty easily.
When strafing, don't get obsessed by trying to blow up the tank. In most cases, just killing the engine is all you need to do. A tank which is not within a firing range, or firing arc, is no threat. The only instance you have to repeatedly attack and make sure its turrets are all dead, is when a tank is already near field or town, and blasting things away. Unless it is something like this, disable the tank and usually the driver bails, and gives you a kill.
.......
So, with bombing, you can kill one tank. With rockets, you can kill another. And with the cannons and MGs, you can disable about three~four tanks with the ammo load.