It looks like this one works pretty well so it’s not needed but if you do still want to buy one these ones work for even the tiniest lamb Adjustable Halter
My dog actually currently has these rashes on the inside of his back legs and they are from environmental allergies.
Not sure what harness you have but if you have one where the strap regularly sits there and rubs get one of these: Halter Fleece they are thicker than the ones for dogs and cheaper (green one is $6.50) to protect your dogs armpits and belly! My dog has no hair on his belly so I bought one for his front clip harness and I love it.
I’ve tried so many fleece covers. Even tried making my own out of fluffy socks and Velcro. I finally found covers that work for me. They’re kind of faux fur? But they’re made for horses! Horse halter fleece covers apparently are things that horse owners use to eliminate rubbing of leather on a horse’s face. I just got a set and I’m so pleased. Just a thought if anyone wants a fluffier alternative to the standard fleece covers. Here’s the ones I bought, if I’m allowed to link: Harrison Howard Horse Halter Fleece Cover Set 9 Pieces https://www.amazon.com/dp/B08SWGM5JP/ref=cm_sw_r_cp_api_glt_i_4P0HE6XNM5JEDCAHPMP3?_encoding=UTF8&psc=1
My hound mix is basically hairless on his belly so when I got a harness for him I got a fleece cover for the belly strap for behind his front legs. Don’t get the dog ones (it’s a rip off) but instead get fleece pads for horse halters. I have this one (Fleece Link) and it’s awesome!! Much thicker and much cheaper than the ones advertised for dogs. Fits my dogs large harness (he’s 75lbs) like a charm, you can cut and hem the ends of you need to!
Don’t be discouraged, my hound is just like this. No matter how many times I work on it he will heel and when releases go right back to the end of the leash. As if he’s walking any faster there than he would be on a slack leash.
My hound has basically no hair on his belly so when I got the front clip harness I also got a fleece to line the belly strap and it’s awesome. Don’t buy one that’s advertised for dogs because they will be $20+ for a thin piece of fleece. If you get a horse halter fleece cover it will be like $4 and the fleece is thicker/more durable (Amazon link).
I’ve also tried everything and the only thing my dog respects is the head collar because he fights himself more than me. But having treats with me on most if not all walks is also super handy. It might seem like treats aren’t a practical long term solution, but if you work on it solidly for a few weeks/months and keep up with the positive reinforcement of “being next to me on a slack leash gets you treats” you should hopefully see some results and can slowly fade out the treats. The key is consistency. Good luck and if you find something else that works let me know!! lol