[FirstYorkie]

The "gradually increasing the time I leave him, not make a big deal when leaving, etc." really will help diminish the barking. In addition, I'd give her a stuffed Kong to occupy herself with (I'd freeze it first so that it takes even longer to get all the goodies out). Also, although I realize it doesn't seem fair to your older dog, I expect containing them together would help, assuming of course that you can trust older dog alone with pup.