We did smack our kids in the beginning, but the more time has gone on the less I'm convinced that it ever helped them. It's far more beneficial to train them how to share, how to behave in the shops, how to manage their emotions, how to handle conflict, and so on through emotional awareness. They just ended up being scared of me when I smacked them. Often they're just tired or overstimulated and they need you to come in and help them cope.
I think I gave a smack a few weeks ago the last time, and even that one I regret after the fact. I'm really thinking to just drop the whole thing.