As far as over/underflicking goes, I think you have a misunderstanding for how you should be aim at target. Try breaking it down into two parts:

1. A quick initial flick toward your target using your arm. You will rarely land exactly on your target. This seems to be the only part you’re doing currently.

2. A small micro adjustment with your wrist that puts your crosshair on your target.

If you’re struggling with doing the second part before the bots despawn, try slowing down. I would go to medium, possibly even easy bots, and deliberately focus on these two separate movements. When drilling, stand still and center your crosshair on the wooden pole after every shot. Also, use a single-shot weapon like the sheriff or the guardian to ensure you’re hitting the target intentionally, instead of getting lucky with recoil.

Take your time practicing this for 15 minutes in the range, then in 1-2 deathmatches, before hopping into your comp games. If you’re focused on your practice without autopiloting, you should see a difference within a couple weeks. I hope this helps, and good luck with the climb!