type of natural finish wood gear. hard wood can be sanded to a fine finish, primed and painted as well though, I have some light oak and darker cherry hardwood in stock that could be made into gears. Also some soft pine that would be a lot less work, and could still be primed / painted. Really soft wood though, if dinged, can lead to paint flaking off. not a huge issue though with non functional gears.
A bundle of branches...no instructions. Maybe make a form like a big cookie cutter. Straight cut and lightly sand ends of branches, maybe 2" in length. Use multiple size branches for variety and to fill gaps. Glue together as you squeeze into the mold. When dry, remove mold. Yeah...think that would work!