I dont like that thing even, and Im train ing a gundog. (I use pinch/choke collars).
When I mention pressure, Im talking about positive pressure, in which the dog learns how to turn it off, and the pressure is a mild to moderate discomfort depending on the dog. Also I dont just assume the dog has learned it just because he did it once, I have to do it over and over and over and over again to make sure he has really grasped it and can recall it the next day. If he falls back, I go back to it again and re-teach it.
I think the worst thing I do is probably toe pinch during FF, in which a string is looped around is two middle toes on his front paw, and I dont tug hard, just enough to cause a mild discomfort, but nothing that would cause a yelp or damage. I also offer lots of praise with this training to make sure my dog keeps a positive attitude throughout training.
Again, Im against this prong collar.
-Dix