Extinction is when a dog repeats a behavior and does not receive any positive response and once he realizes this, he stops the behavior. Dogs are very needy. They will always be doing things to get good stuff for themselves. They are hedonistic! But this works against them when we train them. Ideally, this is the way to get rid of barking.
"Attention" from you can be something as simple as eye contact. Even what you would consider negative attention (like yelling or swatting) is still good attention for them. When using the extinction method (works well for jumping, nipping) I tell my clients to completely ignore their dogs. No eye contact, arms crossed, no physical contact. The next step is to walk away and shut the door behind you. But those of us in our apartments don't have the time frame to achieve our goals this way.
If an immediate cure is needed, please get citronella or sonic collars. Shock collars are incredibly painful especially for little guys, it doesn't matter if you can turn it down. Also, they can cause matting around the neck where the prongs are. Most long haired dogs have to be shaved on their necks. Also, I saw a client whose dog's skin was infected and smelled like rotting flesh from the prongs.
A lot of times sonic collars don't work, especially when persistent dogs just fight through it. Citronella can be the same way too. I recommend the Remote Trainers because it's easier to actually have control in your hands to train the barking out of the dog. Make them realize that being quiet gets them much better things than barking, which gets them a corrective tone. The auto-pilot ones are just cruel in my opinion...>_>
I'm also a Certified Dog trainer, so I'll help in any way I can. Barking is always a huge issue with our terrier friends, but we love em!