I highly recommend the gentle harness. If your dog is pulling on walks, these harnesses will put a stop to it without hurting your pet. If it works with 200 pound dogs (I have a Mastiff) it will work with a small dog. Eventually they will realize pulling won’t get them anywhere and you can go back to using a regular collar. When using a gentle leader harness or any harness I would leave a collar on just for the purpose of having ID tags on your dog at all times. As far as leaving a harness on a dog, it should only be for outside, I have seen dogs wear harnesses full time and have skin irritation issues because it’s harder to keep them adjusted properly and they just cover more skin, leaving more to get irritated.