I have two very vocal Chihuahuas, one Doberman with a range from bass to soprano and another dog who barks worse than my Chihuahuas. She's still in training. The other dogs, the two Chi's and the Dobe will stop pretty well when I tell them "enough."
I wouldn't dream of spraying something at my little dumplings. I think that would be very mean. And possibly injurious to their sensative nasal passages and eyes. Their nasal passages are used for cooling the brain. I wouldn't want that harsh stuff going into them. And it just isn't very nice to do that to a dog. That said....
How I trained my dogs was to go to them after letting them bark a little bit. I'd tell them something to the effect of "thank you" (for the warning) and then distract them. When they stop for even a breath, even for a second, I'd say the word, "enough" and give them a treat. Repeat as needed. Associate the stopping of the barking with the cue, "enough" or "quiet" and reward lavishly. Do not say, "enough" while the dog is barking or she'll learn that enough means to bark. Wait for a quiet few seconds. Later on, once the cue word is definitely associated with the quiet, you can try saying "enough" while she's barking, but make SURE to get her attention on you. You have to go TO the dog, not yell from a distance. Sometimes hollering makes them think you're just joining in in the chorus. LOL. So, for a long time, you have to be very consistant and persistant in going to the dog, distracting, waiting for a couple of seconds of quiet, saying the cue and praise/treat lavishly. Keep it up. It is not an easy thing to teach because the barking in itself is fun. They love hearing themselves bark. So, you have to make it better for them to stop than to continue.
My dogs aren't perfect, but they're much, much better. Chulita really does stop right away. The others....sometimes I have to still go to them when it really is something "bad" outside.
