Gunnery really hasn't changed, just everything else that it rely's on has.
Icons, range, visual cues, hit sprites are all changed/different.
So for some people gunnery is still very similar for others I suspect its a relearn from scratch.
My advice, go back to basics, start in a spit/zeke, get close, blow em up.
Relearn how much lead, distances, etc.
Then work your way back to your fav ride.
No its not easy, but hey, its made a whole new game out of it in many respects.