Dozens of citizens have reported this method worked and it has also worked for me on one occasion.
Anytime a K-9 is deployed to search your auto, announce loudly and boldly that you are aware police can make their K-9 false alert and you know what a true alert looks like. This scares the officer and after hearing your stance, he will usually walk his dog around the auto and then leave.
To learn the difference in a false alert and true alert, watch the two, ten second videos here. One is a true alert and one is a false alert.