Could you suggest a dog collar that would be good to walk a 100+ pound 1 year 4 mos Great Pyrenees. I have tried gentle leader, slip on training lead (thick yacht rope) and harness. The former two created new problems. The harness is good except when he becomes over-reactive to situations. Then, it’s a struggle to hold him. I have only been working with your training techniques for several days. Thank you.