How much / what kind of oil in cylinders for storage?

Turning it regularly is important, IMO....don't 'park' it at the same place each time. Moist air getting into the open valves will do the most damage. Respray in some new oil from time to time. If it will be setting reeeally long, then there are oils used in the aircraft industry that are made to fill the cylinders for long term storage; check Aircraft Spruce and Specialty in the PNW.