When you know where the target is and where it's going, you don't need to see it under your nose to hit it.
What he needs to do is just practice self control. Don't fire the trigger until you're close. Until you're SURE you can't miss. Don't spray, and if you feel even a hint of praying (any uncertainty means you're not 100% sure of your shot) then just DON'T FIRE THE GUNS! Keep fighting, manuvering, positioning until you KNOW you've got a kill shot.
Try flying a plane with crappy ammo loads. All those RTBs with no kills under your belt will reinforce your self-training, and when you finally land any kills you can know you held your fire until you had a GOOD shot. This is very much in agreement with Ghosth's comments.
I agree with parts of this- and disagree with primarily the last part.
I agree completely with the "get close" aspect. And I agree with picking your shots, and waiting until you're sure the shot is a good one (one you can hit). And I agree with the "no spraying" aspect.
I personally hold my shots to D200. Maybe D400 if I'm too slow, and the guy is pulling away, and I'm trying to scare him into turning. Maybe D400 if I'm closing fast, and don't think I'm going to be at my "sweet" range of D200 long enough . I may begin shooting at D400 on bombers too, since I know I can hit them, and want/need a bit of extra firing time. D600 for me is simply to score a few pings and hopefully influence my opponent into a turn. He's getting away, and I need him to turn so I can get closer and have a better profile for a shot.
As for picking your shots, waiting for a good one, I agree there too- mostly. I would definately try to set up some nice, high-probability shots, then aim carefully, shoot carefully (in small bursts) and appraise the result. Adjust aim a bit, and try again if needed (and it probably will be). Paying attention to the shot situation, making a judgement on aim, and testing your hypothesis is really the only way to learn. If you miss, try a small adjustment, and see if that helps. If not, adjust again.
Spraying is bad for a few reasons at least. One, it wastes ammo, and it also doesn't give you the crisp feedback of a small shot-stream. With a long stream for your target to fly through you do have a better chance to score a few hits. But you won't figure out the aiming, leads, etc nearly as precisely, since you won't know if you hit him with the beginning or ending rounds in that long stream. In a long stream you're probably also varying your G-loading, which plays a huge factor in aim-point as well.
However- waiting for the perfect shot will get you killed, especially at first. It'll cause you to miss opportunities that good shots could have been used effectively, and maybe that was your only good opportunity in that fight. Waiting too long can make the fight last longer too, which gives you more time to screw up and/or get joined by other planes (maybe bad guys!) So, I wouldn't wait for "perfect" set-ups, I'd wait for "good" set-ups, and, like in hunting, take the first "good" shot presented. It may be the
only shot presented. Get killed a few times waiting for perfect shots, and I bet you'll get discouraged, lose patience, and start making some bad shot choices. You won't learn to make the tough shots by not taking them.
The last idea is one I completely disagree with. The crappy ammo load idea.
Crappy ammo load planes present several obstacles to learning. One, low ammo count, and two, generally poor ballistics with a weapon (probably some big cannon of one sort or another) that's tough to hit with. Not only is it tough to hit with, it won't help you learn how to shoot the majority of the guns in the game, it'll teach you to shoot with that one oddball gun. Another aspect, is that IMO it can lead to sloppy shooting, since all you need to do is get lucky and hit with one shell. A lucky hit is too effective. Random lobbing can be rewarded with a lucky hit, leading to success, leading to repeating the process... You win that fight, but learn a bad habit.
The biggest detriment IMO to a low ammo load is the reduced amount of shooting possible. I know the theory is that low ammo count will lead to a more concentrated effort to aiming. It also leads to less practice. Practice makes perfect. Less practice makes less perfect. No practice makes no perfect. A .50 cal plane with a large ammo count will give you about 13-16 seconds of practice time per flight. That's about the best you can do. .50s are easy to hit with (positive reinforcement), but require a concentrated fire on a small area (spraying won't work so hot- neither will firing under high or differing G-loads). They also shoot "flatter" making hitting easier at varying ranges, but again, require concentrated firing on a small area (limiting effectiveness to near convergence, which I recommend you set close, say 250-300)(I'm talking wing mounted guns). Unless you hit the pilot, you won't get as many "golden BB's" with .50s as you do with cannons. That's a good thing when learning, it''ll force you to concentrate. And you'll have enough ammo to practice a bit. The time to limit ammo is after the basics are learned- when you're trying to refine the behavior. Not when you're learning the behavior.
Get close, take careful shots, practice a lot, and pay attention to where you miss and why, so you can correct it next time. Look for your general trends- do you shoot too high quite often? Not lead quite enough almost all the time? And don't shoot at the enemy plane. The easiest way to miss a deer is to shoot at it. Aim for a specific point on that target. I personally aim for the spot the windscreen meets the cowl if possible, and pick a different target if it's not (wingtip?). If you're just shooting at his plane, you're not concentrating enough. And any hit on that big area will serve as a "success". If I aim at the cockpit, and hit the tail, I screwed up, and will mentally try to correct for that next time. Sure, I may have won with that tail shot, but it was luck, not aim... If I aim at the cockpit, and hit it, I get a big explosion (positive reinforcement). If I miss it, but hit the engine, wings, fuselage, tail, it registers in my mind as an "Oops, better fix that!", but also teaches me where I screwed up (not enough lead?) so I can adjust (visual feedback, which my tracers will give me if I
really mess up).
Lots of reading, sorry. Skip it if you want...