Loose lead walking, like most behaviors, is best taught with all-positive methods, but the process is slow and tedious and requires time and patience. Pulling on a leash can be stopped quickly and effectively by using a prong collar or some other corrective collar. So why use the more difficult training method? I recommend using both for different reasons and in different circumstances.
The advantage to positive leash training is that you can teach a puppy or dog to heal and to enjoy it. It's a good bonding experience and teaches pack leadership in a fun way. See our page on leash training for details. I recommend that only reward based training be used in training sessions.
However, properly timed fair corrections give a handler and a dog a chance to get out and enjoy a walk without the amount of concentration that a training session demands. If using positive methods, the dog must be constantly paying attention to his position with relation to the handler and the tautness of the leash. Most dogs do not have the ability or the desire to pay attention for long walks, even with a lot of rewards. The handler must be concentrating on keeping the dog focused on the task. Neither dog nor handler have the opportunity to just relax. I don't believe that every walk needs to be a training session. Both handler and dog can enjoy a walk without thinking about the leash if mild corrections from a prong collar are properly used. Read the details on our Collars page for details on proper use.
Neither dog nor handler needs to concentrate on leash training when a prong collar is used. The dog has the freedom to sniff and look around instead of focusing on how taut his leash is. When the leash is too tight the handler feels a slight jerk on his arm. He can respond with a very gentle pop. A correctly administered collar correction doesn't need to hurt. It is only a mildly uncomfortable reminder. It shouldn't hurt the dog any more than the pull on the leash hurts the handler's arm. The dog will re-position himself and the handler and dog can move happily forward until the dog lets the leash get too taut again. Neither dog nor handler is being hurt. The dog is barely putting pressure on the leash before the handler gives the correction. The correction is small, just a reminder. Both handler and dog can enjoy the walk or run.
Don't let all your walks become too leasurely without affirmation. To have a happy well-behaved dog, you need to have sessions on a leash with reward-based training. Always make sure that there is considerably more positive interaction between you and your dog than negative. Praise him when he looks up at you on your walks and walks politely by your side and more often than not, include treats or play rewards. Some correction based training is okay but don't let it get unbalanced.