1. Turn tracers off.
2. Go offline, and practice on the drones until you can generally 'one-pass' them and attack them from different angles, not just the dead 6 oclock position.
3. If you are scoring hits without obvious kills, check your convergence... generally, I put my P38's cannon 50 ahead of the MG rounds. IMHO, the faster the plane, the closer the convergence as your rate of closure will be higher.
4. After a time, you'll notice the planes move in slow motion as you fire... focus as you shoot until this happens.