Air-dry clay i have worked with it in school

Air-dry clay i have worked with it in school in sculpting class, we have worked with clay that air dries OR you could put in in a kiln. but we all did air dry. it gets hard very fast if you dont keep small loose pieces together. but it is very easy to sculpt when using a bit of water. what we did was that befor the end of class, to keep it wet, we would take wet paper towels ans wrap it around our sculpture comepletely. they stay relatively wet untill the next day. i would think it is easy to use but needs to be taken care of properly.