Well for one, they don't get a treat if they don't do it right:).
Let them know you have a treat for them, then don't ask for the full stretch right at the start, just work them slowly, but reward ONLY AFTER they do it properly.
They will get the hang of it. Maybe some would take longer. Harley is just excellent at whoaing when you tell him too. He came that way, I can't take credit for it, altho I've made him stay that way.
Becky
Jake is really good about standing still for stretching. Blade (maybe cause he is still a youngster) has a harder time, especially when there is a treat involved! I have not tried doing it with a treat cause he does not seem to be able to concentrate on anything BUT the treat. I will try it though. He is a smart boy, just loves his treats.