In dealing with a high power dog, I think the worst advice I've ever received (and given) is "you can always take it out of em, but you can't put it back in". While this is mostly true, if you don't get these types under control early, you probably won't ever get it done. The problem is, it takes experience to recognize what you're seeing & to develop the confidence in your judgement to apply appropriate but sufficient corrections. "Nagging" by increasing punishment too slowly, only serves to build their resilience to pressure. This is often the case in those dogs you see who creep at every bird then scoot back to heel. I've seen and heard of absolutely abusive methods used to address this but really haven't seen any work once the habit is formed.
What I do think can work, is to turn the dog over to a Pro who can establish a totally different relationship w/the dog thus getting the dog under control for him, but the change usually doesn't transfer back to the owner, at least not long term. Unfortunately, you don't know what you don't know, therefore most of us have to screw up a dog or two along the way.
