You can also try using the German planes that carry the air-to-air rockets (WrGr-2 I think). They are "flak packs" just like the puffy stuff. You can use those to de-ack. Just fire the rockets at about 1.5k out and they pop shrapnel out and kill the ack. So, in reality, you just need to get them close to the AA gun position to kill it.
A squaddie and I took the bf110-g2 with the regular cannon load-out (the one with the 20mm and 30mm cannons and no bombs), and strapped on the 4 WrGr rockets. We de-acked the field with the rockets and pretty much gunned down the rest of the town except for a couple of buildings. So what I'm trying to say in my ramblings is try the 110 or one of the 190's that carry the WrGr rockets for de-acking and strafing, you might have better results. For aiming most rockets, use the bottom of the sight pipper for your rocket placement. Judging the range takes a little practice. The "bottom" of the sight pipper I am referring to in the picture a few posts up, would be the spot where the tiny hash marks (range ticks that go from top to bottom) meet the circular edge of the bottom of the sight. I personally have very good hit % when I use that spot for my rocket sighting at long or typical firing range. I'm sure someone else may disagree, but, that what works for me.
Good luck.

A8Chustr