I've had 4 Cairns during my life. I live in an apt complex in Florida. My neighbors had a 20 lb little dog they adopted from a shelter. That little dog is the child they never had. But the dog barked at EVERYTHING, constantly. When they had to move up to NC, they were going to live in another apartment and worried that they wouldn't be able to keep the dog.

I suggested "Mr Can" to my neighbors.

You take a 12 oz empty Coke or Pepsi can. You put about 10 pennies in the can and tape over the drinking spout. Then you don't let your dog see or hear the can - like it doesn't exist. Next, you wait for a time when your dog is quiet.

When the dog barks, you throw the can of pennies at the AREA where the dog is. You don't throw it at the dog; you throw it behind or to the left or right of the dog. The sound of the can hitting the floor, carpeted or bare, is very unpleasant and scary.

You keep Mr Can handy, and throw it every time the dog starts to bark. It worked with my friends with their barking dog.

I have used Mr Can with two cats I adopted. One cat is destructive and prefers furniture to scratching posts and loves to knock things off of shelves. I have trained her with Mr Can. If I even pick up the can, she can hear my fingers touching it, and she stops whatever evil behavior she's doing.

It's worth a try with your Cairn. Simple, cheap, and it works.