Picturing the St. Bernard throwing his paw around made me laugh and reminded me of a lab we had when I was a kid. He, too, would throw his paw at you for almost anything--food, attention, play time--I really miss that dog.
Anyways, I'll give shake another try with Dudley. I tried the method of putting him in the sit position, but even then, when I lifted his paw, he would lay down. Who knows