To sign train, take both hands, extending the middle and index fingers. Take your dominant hand and rub the fingers slowly down the same fingers on the non-dominant hand. It is like your fingers are a train, going down a pair of train tracks.
Make the sign more vivid by making train sounds as you teach the sign. "Chugah ... chugah ... choo ... choo!"
When presenting the train sign, make sure to make the accompanying sound effects. “Chugah … chugah … chugah … chugah ... choo … choo!”