What to do when dog refuses and growls at compulsion?

I had the same problem with my beagle. He was always challenging me as if we were rivals.What always worked for me was a quick sharp poke at his neck like a simulated "bite" as if I was another dog.I never hit him or slapped him with a leash like so many people told me to do this just causes more tension and fear. Are you working with a professional at all? If there's a Petsmart in your area they offer obedience workshops that are very useful.I hope everything goes well.