The problem with teaching children explicitly is that we are rarely aware of what we are teaching them implicitly.
For example, if you tell your children to say "thank you," the implicit lesson is that expressing gratitude is something they should do whether they feel like it or not — not something that comes naturally.
Better to say "thank you" yourself — to model the appropriate behavior joyfully. Joy is attractive and, eventually, they'll want in on the fun!
Your child doesn't internalize what you say as much as the energy with which you say it. Pay close attention to how you feel and you'll notice that teaching often carries a subtle vibe that feels "yucky."
So when you must teach explicitly, clean up your energy first. Otherwise you might be teaching the wrong lesson!
When you teach by example, you are following the advice of Gandhi who said, "you must BE the change you wish to see..."