Our Buster would bark and yelp when we confined him and he couldn't be with us (either in his crate or in a washroom near our family room and kitchen). We tried the coins in the can, the spray bottle, and tapping him on the nose; nothing worked.
We bought a PetSafe Stationary Bark Control Device (
PetSafe Stationary Bark Control Device PBC-1000 Kennel Vet) and it has worked VERY well to curb his barking.
If you read the reviews of this product on PetSmart.com, you'll notice that there are a lot of people who have not had success with this product, including a Yorkie owner or two. It seems from teh reviews that sometimes the dog is too stubborn to learn, and sometimes the machine is not sensitive enough to correct the barking.
The good thing is that the machine has a manual button so you can trigger the ultrasonic sound when you hear barking, even if it doesn't get triggered automatically. If you have a barker, I think it is well worth the $25 to give it a try.
If anyone thinks this machine is unnecessarily cruel (and has an idea of what would work better), please let me know.