I knew the frowning and smiling things... I guess only four to slap makes sense though because you just have enormous arm muscles and the face is so complex and- *nerds loudly*
True, true, plus it makes sense. You're just using your arm, and depending on how you slap, your wrist /nerd
So basically the most efficient thing to do in any situation is to keep your face straight and smack someone upside the head