Hi I need some guidance
So I have an older dog, he was a rescue and has some ptsd from before I got him. I have been training him but I can’t figure out how to train him so he doesn’t get annoyed by people and children. He’s good with kids I know and have been around me but when strangers pet him and lean over him he growls and has a few times nipped. And I don’t want judgement I’m genuinely trying to help him but he has broken skin a few times they’ve been in our yard when he has so it wasn’t out and about he attacked someone but typically he gives a few warning growls and then nips and sometimes he breaks skin but majority he doesn’t he just gently taps them with his teeth or mouth area. What do I do to help break that cycle? I don’t have the money for like a full on trainer and stuff but I take him places and he’s fine he does have a hard time with other dogs but I keep him at a safe distance and make sure to reward good behavior when he’s interacting with dogs. But when he’s in our yard people just lean over him to pet him and he growls or stays away from them and they don’t listen to the signs he’s giving. I’ve witnessed a few times where my brothers friends will taunt him and stuff and I’ve pulled him out of the situation. But with the nipping and drawing blood how do I help correct that behavior? I’ve done google research but nothing I find helps.. so can someone give me something that you personally know has worked?
Edit: Just to clarify, I do have a muzzle for him and we use it when appropriate. I also currently keep him away from unfamiliar people when they come into our yard because I know there is a bite risk. What I’m asking for is advice on how to actually work on the underlying behavior so that eventually I don’t have to remove him from his own yard every time someone unfamiliar comes over. I’m not looking for advice on how to ignore or excuse the behavior. I’m specifically asking for training techniques that have helped other people with similar reactive dogs.