How to Stop Lunging Behavior

My nine-month-old Bouvier puppy is in training, but I am having trouble finding a positive way to stop his lunging; he is very strong. I am using a choke chain, and my current trainer feels I'm not firm enough in my corrections. I don't feel comfortable using the choker, but also don't like the idea of the Halti because it might be even more dangerous if he lunged.