Load up a free for all, radar on, like 6 to max bots, mixed difficulty. Put the health to 200hp, there is a setting with ammo carried, put that to max. Bump your sensitivity a little higher than you usually play, lower ads sensitivity on low zoom weapons just a tiny bit - keep it above .80 however.
Anyways yeah keep killing bots for a LONG time. Like maybe do 100 hipfire only kills to help with your centering, after that allow yourself to ads to practice aim. Lower your sensitivity after you are done and when you go into a pub you will feel like you cant miss.
Make sure controller vibration is off btw, having this on in pubs will always make you inconsistent.