It's about getting as stable as possibly allowed by your position, controlling breathing, controlling the trigger, and holding through the shot-or recoiling the same way each time.
Part of it is teachable, some of it isn't, and there's nothing better than trigger time-including dry-fire practice.
Double-set triggers are a delight for dry-firing practice-with their "independent nature".
The point with dry-firing practice is for the student to concentrate on achieving good target and sights alignment AT the moment of trigger release and HOLDing that sight picture as long as possible
after the trigger breaks (follow-through). The job for the coach is to watch for any flinching or inconsistencies in position, watching the breath.
Dry firing from bags the sight picture shouldn't change at all in follow through. If it does there's a hold, bag, or flinch problem. But this isn't about that.
Or something like that. I'm not a shooting coach but won some stuff a few times-especially off-hand.