Have you used, curently used or even considered a harness, gentle leader, prong (pinch) or E (shock) collar? If so, most likely your dog still manages to pull or eventually will. When I first meet someone utilyzing one of these marketing masters, I take them off their dog and begin to show them what the dog should be learning and can learn to do-without. It's amazing!
You see these apparatuses manage to contribute to the behavior of pulling on the leash. If it's uncomfortable or harsh, we are communicating negatively to our friend. Rather, comfortably reinforcing a dog to no longer pull but sniff the grass along the walkway fulfills an instinctual need and relaxes them. As for the harness? Just like when I tracked with my Police K9 he wore a harness. After teaching him to keep his head down initially, we reinforced sniffing the ground by playing a"push/pull" game that utilized the harness. As the Police Dog pulled with interest in the scent, he was met with resistance having to pull my body weight. Therefore, he worked harder to maintain the scent. The harness fits over and around the dog's areas of strength; shoulders, back and chest. This helps him to have the stength to pull. When the dog reaches the end of the leash we tend to correct or pull back. Here begins the "tug-of-war" game, reinforcing pulling.
Using a regular dog collar will work just fine and it will feel more comfortable. There are positive ways to condition your dog to listen to you and be near you,which may then be rewarded. Trust me, you will be more relaxed and this newfound feeling will pass through the lead to your best friend. Would you put one of these devices on your best "human" friend? I didn't think so. Seek a qualified and proven dog trainer to teach you and your dog to walk on a relaxed leash out in front of you. You both will breathe a sigh of relief!