Mekuti dog harnesses are well reviewed by some trainers. I've never used a harness with any of my dogs over the past 46 years. Until my current spaniel joined us aged 10 months. She was a real challenge to loose lead train, spaniels are so scent driven, getting their attention, their noses up off the ground and focussing on walking nicely by your knee isn't something they're particularly keen to do.
I bought a Mekuti , I used it so she could sniff and explore on the end of a long training lead - teach recall and how far should should every go away from me. It also helped on pavement walks, to teach loose lead walking. She's brilliant now, a whole year later.
The main thing though, is harnesses are usually used for sledge dogs, to help them pull. It sounds as though your dogs are good at training you NonnaW. I empathise