The mutt's nuts
First get your excitable (and in this case) very large dog by the scruff of the neck. As he squirms, grab him by the - oh dear, I was going to say by the balls, but in this case, where his balls should be .. and massage vigorously (I kid you not).
Unsurprisingly, the dog collapses on the floor, eyes glazed, soppy look spreading all over his face.
Repeat at frequent intervals until balls descend.