Hey, I have a 10 month old black lab that I am attempting to train myself, we are learning duck hunting together. I went out and shot a few ducks first, and let her smell them in the backyard. I then hid them various places, let her smell my hands, and told her to "hunt them up." She immediately goes to work and sniffs the ground and air, and finds them extremely fast. I took her to the woods hunting today for the first time and once a duck went down in the water I told her to hunt it up, and pointed at it. She jumped right in and brought it back and dropped it, I think it's mostly instinct for them. I retrieve toys and stuff with her all the time, and when it came time for a real duck she just seems to know what to do. I have no doubt she could smell out ducks (or deer, hogs, whatever) lost in the brush.
The biggest problem I have with her is the basic stuff, like waiting for the ducks to fly it is hard for her to stay still and not want to go track everything in the woods. I kept her on a short leash tied off, she just doesn't like being on the leash. I guess they are like little children, they just have a hard time sitting still.