You can practice shooting the ack in the TA in the dive bombing area. If you can manage to shoot down all town ack in two passes with 10 rockets, you are good enough to even bother taking rockets with you in the MA. Just practice a lot and try to find an optional sight that fits your needs. Getting all the town ack in one pass and 7 rockets is hard but its possible. Take a couple hours doing just that and you will become good at it.
Usually, I shoot my rockets by simple instinct (just "feel" your speed and dive angle) and 90% of the time, they will hit the target. When i'm not sure if a rocket will hit, ill just shovel one more at a slightly different angle in the most likely target's bulls-eye direction.
Another good trick to not get shot yourself by the ack (either with rocket or gun passes) is to predict when the targeted ack will fire and at the same time pull up and down slightly to make its rounds misslead you. This will double your chances of survival in a close up gun pass on a field or town. If if pass about 100ft above one that you missed, you are pretty much screwed as well. So, prioritize the ones you know you must pass over once your attack run is done.