I'm not going to call myself a "trainer" - but I spent a couple of decades teaching horses (and their riders) how to be "good". I've also convinced a dozen or so dogs to be great pets.
I apply a principal I've always believed with horses: put them in a bit that will stop them in their tracks; then ride with super-gentle hands. Example: a halter is very comfortable for a horse to wear - but if that horse decides to take off with you on its back, you won't be able to stop it. They are too strong.
Now that I'm officially an Old Lady, Augie is stronger than my hands are able to hang on to the leash - I found that out one day while walking him; and as we approached an even older lady walking a small dog, I went way off the path and told Augie to "sit". Which he did nicely, until the lady stopped in front of us and proceeded to coo and baby-talk him until he simply lost it - ran like a crazed dog towards her, ripping the leash out of my hand, jumped 5' in the air and as he flew past her face, he gave her a sweet little kiss on the cheek!, landed and ran right back to me. THAT is when I realized I needed more control, and ordered the prong collar. And like I said before, now that he is used to being quiet and polite while walking, he continues to be good even if he doesn't have the prong collar on.
I DO have a Sprenger "no pull" harness that worked nicely on him as a pup, but as his fur grew longer, it got tangled in the harness and was inflicting discomfort for no reason.
Just some random thoughts....