Monorail or Field Camera ?
Most parts if kept clean are better off with-out any lubricants as the amount of use / movements will not cause much wear, however you can spray some Silicone onto a rag and apply it sparingly to moving parts, often it is the rails that rub together than need some lubrication, not the gears. Grit, sand or dust in /on gears is bad so do not use oil.