I wonder what your objective is in giving this workshop. Are you trying to attract new people to pottery? Are you trying to teach a particular technique? Is this a fundraiser? Will your participants be signing on for the full 6 days?
Don't use anything that contains asbestos! Although you might use a good mask, asbestos fibers can linger in your studio and on your clothes. They can be lethal.
My brother, a chartered accountant, worked in the office of a company which made nuts and bolts where asbestos was used on the manufacturing floor. My brother rarely visited the manufacturing floor. He died of mesothelioma. It is not worth the risk. Mesothelioma can appear more than 20 years after exposure. My brother was in pain, became paralysed and eventually lapsed into a coma. Please don't use this stuff.
I once had a customer ask me why bowls were always decorated on the inside. She had a daughter in a wheelchair who only saw the tableware from a low angle and found the outsides of bowls very boring. As someone else said, it depends. Lin