Just to add one more point on the "site picture" concept. If you are spraying away 200-400 behind an nmy and get a few hit sprites, you really have no idea where your aiming point was when those couple hits were fired. OTOH if you burst, pause, burst, pause, and one of those bursts yeild hits, you know what that site picture looked like when you fired.
Now if you look at a film of somebody like DMF you will notice he usually fires short bursts very effectively. He seems to have a library of site pictures in his head that yeild hits, and doesnt often fire until seeing one of those site pictures.
So I think in some ways the key is not going for every possible shot you see, but instead looking for shots that you are good at to develop. Dead 6 shots are hard. I usually fire very short burst at that site picture for 2 reasons. One I may get lucky and find the right aim point, but more importantly I am looking to force some maneuvering on their part to give me a site picture that is better for me to hit. Part of gunnery is setting up the shot.