Peanut Butter Stress Fix
When I have to take my older dog, Nova, somewhere where she will be stressed (such as a class with many dogs outside, or the vet) I have found it very useful to put a wad of peanut butter on my finger and then smear it on the top of her mouth (inside!). She is distracted from her stressor as she licks it off the roof of her mouth. The same trick might work with stuffing peanut butter into a hollow toy, too!
Certainly, conditioning her to work with the stressor is better, but for a short term fix, I have found that this works fabulously for my dogs. How do you destress your dogs?