If they get gritty (e.g. rain spattered sand) you can wipe them off with a soft cloth, perhaps dampened with ATF if you need some moisture, but it is not necessary or desirable to lube the shaft. However, some Power Gear jacks have a grease fitting (zerk) on the collar at the bottom of the cylinder (where the ram shaft slides in/out) and a occasional squirt of a lithium grease is needed there to keep the jack running smoothly. If you don't grease that zerk, eventually the jack will retract slowly or not at all. Other models are permanently lubed and have no zerk on the cylinders.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL