Couple of points on killing acks.
On a small field in a fairly nimble plane you can kill most of the ack in 2 passes. Take one side of the runway first, extend out of range, zoom up, dive in on the second.
Then clean up VH & any you missed.
Slower is better, jink every 2 seconds, even a minor one. A pure roll won't do it, need to deviate your flight path slightly.
So roll 10 degrees push down, shoot, pull up shoot, roll back center, shoot, jink up, down, left right, rudder etc.
Cannon armed AC will kill an ack with a single hit. Or some guys like the p47 with its 8 .50's that works almost as well.
Mostly its practise, practise, practise.