Hee hee - staffies! Remember - he's still only a baby and still teething! Make sure he's got lots of (safe) chew toys as an alternative to your fingers, and they yelping thing seemed to be the most effective with my two. I would try and keep it consistent and use only one method (he may be a bit confused!) Bear in mind, he will go through a secondary chewing stage too! My two are nearly two years old now, and the boy will still have a little chew if he's over excited (girl is an angel and so calm by comparison!) Wouldn't change either of them!