Yes dry, but preferably in something like a bowl or a cup, deeper than a plate. Some people fasten a cup to the side of the pen, so it can't get knocked over.Does that mean putting some of the powder in a plate alone? Or does it mean putting some powder and adding some water then mixing it and leaving it on a plate?
The difficulty is to know how much calcium is right. If they seem to be doing well, then you probably have an amount that works well enough.What I am currently doing is giving all ducks and chickens the same feed, which is a mixture of duck food and the usual dried corn and some calcium powder mixed with it, so I am sure that all of them are eating calcium.