It's not necessary to mist him at all during shedding. It can cause problems. Once I realize mine are in their shed cycle, I generally just leave them alone entirely until they shed.
A humid hide is just a hide with some damp moss or something in it to increase the humidity inside the hide. It gives them a place to go if they need it to be more humid to help with their shed. There's some threads around here somewhere about creating one. Should be able to search for them or google it.