Pulling in our harnesses is from a tight fit (over-adjusted chest strap) and or from pulling back on the leash.
Most dogs that have been pullers with other equipment will often forge ahead of you if you start by standing beside your dog with a loose leash.
In this case, do not pull the leash backwards. Instead, hold the leash steady and stop walking. Then step out to the side (to the right if your dog is on your left). Stepping to the side gives your dog a cue with the harness to at least turn his head toward you. If you reward his response (treat and or verbal praise), he will learn to respond when your leash begins to move to the right.
We recommend starting in front of your dog to make the best use of the front leash connection and to hold the leash as close to your dog’s head as possible to keep the slack out of the leash. If your dog is distracted and gets in front of you, start by facing him and step backwards to keep his attention.