Deacking in a plane with cannon and rocks is not tough....or even with just a plane full of rocks...i actually enjoy doing it b/c of the satisfying boom

Take 2 P38Ls with rocks, and scissor back and forth across the field starting from 8-10K. Stay above 3K using rocks (1 per gun)...usually you and your bud have killed 12-20 guns with just rocks. after 4 or 5 passes.
Continue with cannons when rocks are gone by jinking on ingress and egress so the auto tracking auto guns have trouble hitting you. You'll take a few hits, but, hey...you have TWO engines!
(note - does not work with an LTAR, Zazen, or any other skilled shooter in a manned gun)