I got my chessie Male from the humane society. He has around 400 ducks under him, and its only about half way through his second season. He is almost three years old now. This dog was absolute hell for the first 6 months of having him. I wanted to take him back SO many times.
Can it be done? obviously... Is it easy? Nope. It just depends on how patient you are and which dog your talking about.
I personally will never get a dog from the pound for hunting again. It was a lot harder trying to make him into what I wanted vs. Just getting one at 7 weeks and molding him into what I wanted. You know the health and background when you get them as a puppy. This is important with all the displastic dogs running around.
All that said, I wouldn't trade my chessie for anything. He is an absolute pleasure to hunt with.