I've read that with the Cans and Sprayers, that the dog should NEVER know that it's you...it has to seem like a total mystery...That's why I never tried that route, since I think yorkies might be too smart for a trick like that...might work on a golden retriever, but not Chewy.
Oh, BTW, UPDATE:::
Chewy now "speaks" on command. He learned it in less than 24 hours. Awesome little guy! So now I turn on the flood-gate with "speak" and get him really barky, and then turn it off with "hush" and only give him the treat when he's been quiet for 3 seconds. As we train on this, I'll do it with people at the door and other "barky" situations. So far it seems very promising.
On another note: Chewy is acting a little wierd...I think it might be what is sometimes called an "explosive extinction" or something like that. It means that as he has finally learned to modify hisbehavior, he is now doing it TWICE AS MUCH. This is actually a good sign (or so I read). The comparison offered was that of a person in an elevator that doesn't work. After the button doesn't work the first time, they push it several more, harder and harder, before they give up and take the stairs.
It's either that, or I'm screwing up my dog!