Best way to learn to aim is to have the negative reinforcement if you miss.
Fly a 109F4 wiht 150 rds or a yak9u with 120 rds.
You miss, you go home. Flying back empty handed is the punishment. Landing a kill with only 20 rounds fired is the reward. Trust me, that kind of shot discipline more than pays for the time it takes to learn.
P.S. If you're missing and you can't tell how you're missing, you are too far from the target. If you're spraying, stop. Only take high-percentage shots, or keep fighting until you have one. "Get in close, until you cannot get any closer, then get closer still" to paraphrase one German ace.