I'm not a dog trainer by any stretch, so follow my words with caution. Six years ago, my ex fell in love with a pet store Springer puppy. She'd grown up around her family's Springers and had always wanted one. I'd always wanted an upland dog, but not from a pet shop. We all know how these disagreements turn out, and the puppy came home. At some point, I noticed him following scent in the pasture and decided to give it a try. I picked up some frozen pheasant wings a buddy had for working his Brittany and hid them in the pasture. Puppy found them, and we had a new game to play. Find the "bird," win a prize. I have another (older, adopted) dog that heads for the next county if I touch the gun safe, so I started the puppy out with a simple cap pistol that I'd hold and fire where he couldn't see it. He was a little startled at first, but got used to the sharpness of the sound while we played the game in the pasture with the wings. Within a few months, we were launching and fetching dummies and learning the whistle and hand signals (the wind blows where we hunt, so visuals are important as sound doesn't carry as well). I trained him the way I wanted him to be and kept it simple. One whistle blast (hey, pay attention to me), three blasts (come back). Lots of praise, and an occasional treat.
He's hunted pheasants every year since. He had talent out of the gate, and I'm glad that I didn't dismiss him because of his origin. He stays within gun range, rarely requires correction working back and forth in front of a party, pays attention to his party, and has a good nose. He got beat up his first year in the field by a big South Dakota rooster who wasn't quite dead yet, so he won't retrieve birds now - a compromise, since he'll find them for me and stand nearby. I have more fun with him in the field than I actually do shooting the birds. I think the keys to where we are now were his natural hunting instinct, PATIENCE, making the training/games fun for him, and keeping it as simple as possible. I have a friend who bought a GSP puppy over a year ago and has had him at a trainers for quite a bit of the time since then. Yeah, he's a driven dog, but he's more of a robot - not a dog who'll sit on the tailgate with you at the end of the day after a long day of hunting. He has YET to go on an actual, wild-bird hunt. He's great finding caged pigeons in a field, though.
My daughter found a Springer puppy at the same pet store last year. She seems to have a good nose. She points, rather than flushes. I've been working with her the same way I did my six-year-old. We'll see how she does in the field this fall.
It really doesn't get much better than being able to take your dog out with you as your bird hunting buddy.