....If the collar isn’t helping, either it isn’t fitted properly, or it's being used with too much force (a flick of the wrist, administered with the strength of one finger is all it takes) or because the trainer is allowing the dog to lean into the collar or is forcing the dog to pull. Try to remember the next time you put a collar on a dog that you are training dogs, not catching fish.
To my eye, the clearest indication that the owner's pulling problem will be vastly more difficult to resolve than the dog's pulling problem is when the lead is wrapped multiple times around the owner's hand.
That is NOT finesse. That is NOT communication.
That is a clear commitment to PULL like hell.
This is referred to as the Suicide Wrap in horses.