Youngster jumping and grabbing at your hand during a walk-arrgh!

 I am going to come at this from a compeltely different angle. There are two aspects that need to be adressed here, one is the frustration level of the dog and the other is impulse control. Dogs do have needs and for an active breed like a goldie, a walk just doesn't cut the mustard. It is like us watching kiddies cartoons. They need some kind of active on going training to keep their minds busy and well, and they need a set of boundaries to make life ok for them. There is a golden thread that seems to permeate dog trianing regardless of tradition which is to some how focus on getting the dog to shut up and be quiet. I don't think this is ok on any level unless you have adressed the dogs needs for activity and stimualtion.

I would check diet, and wieght. I absolutely expect many gun dogs (and poodles) to do this stuff. I absolutely will not have it happen to me! I ask for four on the floor and develop this behaviour even at high levels of arousal. I will heavily time out for mouthing behaviour with adult dogs but it is pointless when the time out has no contrast to normal life. Simple stuff. Carry it through past extinction. Mouth me, you go away for a couple of minutes. It happens always.,regardless It will stop. The sad thing is that as a 3 or 4 month puppy a couple of ignores might have done it. Now that it is so entrenched and prodcued results, you will most likely have to pull out the heavy artillery.

Jewlieee

 spray ICK spray or bitter apple spray on your hands before a walk.

Also, this is more complex behavior to tackle than just mouthiness on a walk. It sounds like there's no impulse control and that the dog needs an outlet for frustration. So, I would start with training impulse control using commands such as wait and leave it. The owners should practice NILIF constantly for a while and work out some of the frustration by doing free shaping with a clicker.

Agreed.  Usually, this behavior occurs for one or more of these reasons:  1. The dog is bored mentally.  2. The dog is not sufficiently exercised physically.  3. The dog did not receive proper off leash social experiences with other dogs during the socialization period (age 8-16 weeks) when pups teach each other, in play, not to bite so hard.  4. The dog is insufficiently trained - after all, if the handler can preemptively place the dog in a "down" or "sit" on cue, the jumping and mouthing are prevented by means of the dog learning a different default behavior.  4.  What Julie said - just goofy adolescent, almost mature, dog just being a jerk due to lack of impulse control;-)

Here's how I handle this on a walk.  Have a clicker in one hand, and some treats in a bait pouch at your waist (you can use a cheap nail apron, if you want.)  Basically, any time the dog nips, you "turn to stone" immediately.  Don't even make eye contact no matter how unpleasant he is (because your attention is probably reinforcing the nipping, even if it's negative attention).  He doesn't get A SINGLE DARN THING for being a jerk.   About 3 seconds after the dog stops the unwanted behavior on his own, you click and produce a treat for him within one second of the click.  He learns that to get the good stuff, he needs to stop jumping and nipping.  For really confirmed nippers, head halter training may be an option, but please do that with the help of a good positive trainer who can help you acclimate the dog properly to the halter and teach you to use it gently but effectively.  

My dogs have never been forced trained in retrieveing and have never ever failed in trials. In fact my departed dog and now my oldest poodle have such huge retrieve drives now that sometimes it is a little excessive.

I  find that often force training covers up training deficits and often on soft dogs makes the whole retrieving exercise very slow. It is fraught with difficulty. But it is owners choice. It is important to not make jumps as to what a dog is thinking. Working out simple emotions is hard going!! There are other more obnoxious and quite common methods of force training. I often find that the dog refuses or is slow becuase it hasn't quite got the full idea of the exercise.

I personally never have a problem with people working through whether they can keep a dog or not, and working out other options that factor in a dog's welfare. Sometimes you can't keep a dog and that is sad.