My opinion - and as usual it's worth what you paid for it.
I get the impression (from many of the questions you've asked recently) that you are farily new to shooting (at least the AR) - sorry if I'm wrong - no offense intended.
I think you are going about this wrong.
Learn how to shoot accurately, THEN worry about doing it quickly. Trying to learn how to shoot quickly and accurately will only teach you bad habits.
Spend time first becoming a very accurate shooter, and then slowly increase the speed of your follow-up shot and work your way up. I believe that if you do it that way, it'll be pretty easy to accomplish (but it'll take quite a while, and a lot of effort).
A good example of a similar concept - Biathletes don't learn how to shoot while tired and breathing hard - they learn how to shoot under perfect conditions, and then gradually add the additional challenges of biatlon.
Good luck.