My sister has an older dog who i have been taking care of. She is a pit bull mix and she is 11yrs old. She has hip problems, so you can imagine how hard it is for her to sit. She is a highly food motivated dog but she has a hard time with the body positions.
I wanted to do a lot of obedience with her just for practice, but I realized she had an even bigger problem. She was a reactive dog. I decided not to do obedience training and took her for a walk. We encountered several dogs along the walk. She would pull a little on the walk, but she calm down after a while.
I taught her how to walk loosely on the leash first. Then we walked down blocks where I knew there were dogs. As we approached about 25 feet from an all white pit bull behind a fence, she begin to stare. After the stare I heard a low growl followed by her galloping sideways while intensely staring. She then started barking.
I just broke this down for you but this process literally takes seconds to happen. I was working with Tyril Frith, another dog trainer, who taught me some things of how to attack this issue. I started implementing some e collar conditioning. One thing I want to say is that I never just punish a dog with the collar.I condition them
I wanted to work below her threshold so that I wouldn't take her over the edge. The threshold is the line between a dog who is calm and a dog that is wildly out of control. Once a dog gets wildly out of control it is best to excuse yourself and the dog out of the situation because anything you say will go in one ear and out the other.
Back to the walk:
As soon as she even started staring at the dog with intent, I corrected that behavior. The earlier I can correct the behavior the better. After the walk I realized where the threshold for this particular dog was and what level of correction she needed at that level. Next I taught the dog to look at me.( This is very important with reactive dogs). Once she knew how to look at me I used this when encountering other dogs.
The whole idea is to teach the dog what you expect and discourage unwanted behavior. It sounds simple, but the timing is the most important factor in this equation. This dog showed tremendous progress as we worked on this for several days in a row. She would see a dog and immediately look away.
Now that she understands what I don't want, I had to let her know when she did a good job. I can't always focus on the negative or it will ruin my relationship with the dog. I gave her a lot of praise and verbal marker (YES!!!) when she was calm around dogs or she looked up at me. This is a long process but we will continue to make progress as she has.
If you have a dog that is not just reactive, but you know might bite a person or another dog, then I would seek out a professional dog trainer who will probably work through with a muzzle for safety reasons. Stay safe and enjoy the process.