In some cases I use a method similar to the one used by a sniper.
In the event that a sniper misses the target by one meter to the right, he corrects himself the second time by aiming one meter to the left of the target, thus hitting the target.
Makes sense?
Do not panic - no animals are harmed by this method!
So I do the same with some of my swimmers. A simple example, if one of my swimmers' arm movements are like a windmill when swimming freestyle, and accordingly their is very little support out front, I give them a special exercise that exaggerates the arm position with both hands out front.
As with the sniper, I adjust and exaggerate their aim in order to hit the target, and reach a movement that is somewhere in between.
Recently, I had a student who was so precise and conscientious following my instructions that he duplicated the exaggerated movement exactly. He replaced his “windmill action” with an “over-gliding” or "catch-up" one (the intention is that the swimmer achieves something in-between )
I was very surprised until he told me that he was a sniper in the army!
Please Note:
This is a very simple explanation - the method is more complex and I do not recommend experimenting with it without the supervision of a trained swim coach.