Your dog should be conditioned to the use of the clicker.
A quiet place in your home where your dog is relaxed.
Hand your dog the treat or toss it if you know he will come back to you.
After trained, try to maintain a positive association with the collar grab. If you have to use it to get control of them when they are not receptive, make sure you reward them. Try grabbing and then releasing them to go do something they like or were about to enjoy doing.
Practice for about five minutes a day until your dog is comfortable with you grabbing his collar. This may take a few weeks to achieve.
Your dog will happily allow you to grab his collar.
My dog won’t let me near his collar.
My dog will let me touch his collar but when I try to grab it he moves away.