Jeff, one of the naturalists, is working on training them to eat out of his hands. Chickadees are naturally friendly and not very afraid… so it isn’t hard to train them.
If you feed birds in your backyard already, here’s the trick: get them used to a regular feeding time. Only put out enough food that they can finish it off before the end of the day. Put out more the next morning, and the next. Then, once they are used to coming, just go stand there with the seed in your hand.
I heard of one nature center that has an unscare-crow. It’s dressed with a winter coat, hat, and mittens. The Center has a duplicate set inside. When folks want to experience the chickadees up close and personal, they can put on the duplicate set of snow clothes, fill their hands with seed and step outside. The birds take to them just as easily as they do the unscare-crow!