Using wood ashes in your chicken dust bath isn't mandatory.
My chickens have enjoyed any number of dust bathing mediums : peat moss, ordinary construction or beach sand (you probably have access to plenty of that in Florida), forest duff, and compost pile debris compiled of cow manure, garden refuse and their own decomposing droppings raked from their pen and coop.
But here's a warning - you may go to all the trouble of building them a first class dirt batch and they may ignore it for a homely corner of your garden.