I just read the first chapter of a book (online, you have to buy it to read the rest) about training a child.
I do think you have to train a child, at least in some areas, but I'm strongly against pain in very young children and deliberately creating tempting situations where you get a slap on the hand if you don't resist.
One training method was for what to do if a nursing baby bites - you should pull their hair! There are many training and preventing methods for this, that acheive the same result without being mean. I put Grace on the floor and say the milk bar is closed.
The first chaper is here