I am a huge proponent that once you have become proficient in the fundamentals of firearms on stationary targets that you should move into Adrenalized Shooting. So, once you are proficient in the following fundamentals of:

Stance

Grip

Sight Alingment

Sight Picture

Trigger Control

Breathing

Follow Through

Once these fundamentals have been ingrained on stationary targets, you need to begin shooting in a way that stresses the body into triggering the fight or flight response. Utilizing a timer and potentially moving targets is generally an initial step. Placing something on the line like a certification, bet, etc. can also help to increase the pressure. Personally, I prefer to utilize some form of exercises like down ups (burpees), running, weight lifting, obstacle courses, etc. Once adrenalized, you need to manage this so that you can shoot effectively. This is what most closely resembles a real combative encounter with a firearm. If you regularly do this, then you are giving yourself an advantage in a moment of extreme violence, and that is what IRT is all about!