Sharing

When learning to share I started with a 2 1/2 year old and an infant by telling the older one to say, "No, no sweety," and gently take the object away when baby grabbed her stuff.  Now that they are 4 and 2 I have a new jingle to the melody, "Michael Finnigan." The words are: "Trade, take turns, then ask Mommy, trade, take turns, then ask Mommy...This is how we share!" We have seen the picture, discussed it, and practiced it, but they still need help taking turns. The older one knows how to look for something to trade, but counting to 10 while waiting to take turns is still too difficult for them without help. I actually want them to learn to go to an adult for help when they can't solve it themselves. Otherwise one of them gets hurt. How do you teach your children to share?