Mirroring is very important. This should be done right from the beginning when children are learning "Daily Do". For young children, you can be on your knees facing the student with your hands and the student's hands back to back while you are singing and signing. This helps students line up their hands correctly and learn the hand signs a little easier. Students can also mirror each other.
Mirroring can be done anytime during the learning process. Just ask everyone to mirror and repeat what's being learned.