Though I am not familiar with the exact mechanisms in WCS, the manual recommends "MBI instrument grease" - which I hear is simply a version of teflon grease. I am a fan of no grease at all, but if you must, grease very sparingly. I just use some stuff I have left over from my model railroad hobby, PTFE Superlube grease. Its safe for things like plastic gears, its even rated food grade for incidental contact with food, for if you accidentally lick your motors