I have a lot of experience doing sports and combat sports at a decently high level so I just apply the methods of training for those to shooting e.g. breaking down complex movements into parts and training those parts separately as well as part of the whole, periodization, mental imaging/sports psychology etc. These are all things I did for football, wrestling, kickboxing/mma.
So an example would be breaking down the steps of my draw. I typically use a Safariland ALS holster for the matches so I start my draw stroke with indexing my thumb on the ALS hood. I will do a few dozen reps of this. Then a few dozen reps of activating the hood and starting to develop my grip on the gun (typically a Glock 22 or Beretta 96). Then I will follow through with the draw to presentation. I will do this rep scheme from both hands at the sides and hands up front.
I do something similar with my CCW guns which I normally carry AIWB.
I also do similar with rifle/carbine, but most of my rifle and carbine training was from my time in the Army, where rifle/carbine training is ok but handgun training is abysmal even for people issued sidearms.