
I can't use bungee leads at all. I have hypermobility and my shoulders are my worst joint, and despite pretty well-toned muscles keeping the joint together, they just cannot cope with the constantly changing pressure if a dog is pulling on one of those so I end up subluxed (partially dislocated) and in pain. Much better on a normal lead.
But that's just me - I do know people who have found them fantastic for easing the strain with a pulling dog. But, it's still not a replacement for training and no matter what that flash website says, they aren't going to magically stop a dog pulling - just take the edge off it. It still comes down to training, in the end. It always does.
My preferred method for that is 3-fold: 1) when the dog pulls, walk backwards. Literally - keep facing the way you're going, but walk backwards. Keep going until the dog breaks qaqway from trying to go forwards. It's an obvious change. 2) Lure the dog back to your side and into position, turning them round with the treat you lure them with. Reward a few times, but most dogs have the hang of it after 6-10 repeats so won't need rewarding after that. 3) Start walking again, rewarding them when they aren't pulling. This will need to be fast to begin with - the very first step you take - and sometimes every step for a little while until they are staying with you for the next treat. Then you can start to spread out those treats and gradually, go further and further between them as walking next to you becomes the new routine.