Anyway to make your hands full of calluses?

not as weird as it sounds...ha well i don't work as much in the winter and i had like rhino skin hands from doing rock walls and retaining walls etc etc, and its starting to go away and i work like 1 every week so i don't want it to go away because it helps a lot and i don't want to lose it for next year any easy way to just keep my entire hand pretty rough.