FF if done properly is not cruel to the dog. It's part of the training for dogs that will only do a partial fetch or none. It reinforces the command to fetch by making it uncomfortable for the dog if they don't listen. Same with OB. Teaching the dog to heal, you either do a quick yank on the chord.Through repetition it will eventually heel. Yanking on the chord is uncomfortable for the dog. If you use a prong collar its the same basic principle, the pressure on the neck makes it uncomfortable.

In upland bird hunting, some don't need strict obedience in fetching as the hunter can always walk up and pick up a dead bird. But for a retriever doing waterfowl, its main purpose is to retrieve or whats the use of taking it? It is his job and as such, ff is part of the training. There are other methods of training like positive reinforcement (clicker, treats, etc.) but I have yet to see it being done or adapted to field hunting.

You probably saw your friend do an ear pinch or toe hitch. Another method is blowing in the dogs ear or grabbing its hock. Neither of the last two hurts the dog in anyway. An as for the ecollar, I would seriously suggest you think on that one. An ecollar is for when you absolutely need the dogs obedience like when the dogs life is in jeporady.