You can train someone without ever correcting them by narrating what you are doing while you do it. Count your campers out loud and your co-counselor learns to count campers. Say why you are giving a high five and the children start noticing the same behavior. It feels ridiculous the first several times, and you cannot keep it up all day, but it teaches without any confrontation at all.
This is the short version. The full lesson, with the story behind it, is in the book.
Take The Summer Camp MBA with you, or get the field notes by email while you work through the lessons here.