I have heard that part of the foundation of teaching your dog 'quiet' is to teach him to bark on cue, but in practice I don't think it is so easy (I have tried!).
I think a better solution is to determine why he is barking and reward him for not barking. Maybe your dog is barking because he is excited. So you might turn him away from the other dog or distract him with treats and then reward him? And if it is a non friendly dog I also like to move away and ask your dog to do something (like sit, or look at you) and reward. Your dog can't bark when he is eating treat!
I good way to practice is to start dog classes. Even if Scout can sit, down, heel, etc.- he can get used to being calm/safe around other dogs. I also practice by sitting outside of Petsmart/Petco (you can sit as far away from the door as you need to for your dog to be calm) or by sitting a distance away from a fenced in dog park.
If you want to teach your dog to speak anyway I would try to get him really excited by playing with him, running around throwing a ball, playing tug, usually mine will start barking when he is amped and wants me to throw a ball. Originally, I taught Dax to speak by making a weird noise that I noticed made him bark. If you have a dog who barks a lot when he is excited it is very easy to teach them...