ORIGINAL: lostmountainlabs
The hard mouth issue is easy to fix with a good stiff bristled scrub brush...wrap it with a wing on the handle side and throw it out for him the bristles on the brush will teach him to hold it gingerly so he won't hurt his gums. I start all my retrievers out with this method and have found that it works wonders for hard mouths. It's also a hell of alot safer than useing nails or cigarette's.
When I was 14 my grandpa gave me a lab/gsp mixed pup for my birthday. He was hard mouthed most every bird he brought to hand was mangled. grandpa filled a grouse up with nails and tossed it out in the field and sent Reble to retrieve it. he got back to us and had blood pouring out of his mouth. it fixed the problem!!! He never retreved a bird again!! he ran to the bird and put a paw on it waiting for us to come get it. just food for thought. Grandpa wanted to shoot him. he still was one of the best dogs I ever had.