It should be pretty obvious by just looking at that gearbox why it needs frequent lubrication. There are lots of moving parts in there, far more than a conventional or outrunner gearbox. Conventional and outrunner gearboxes have one gear mesh point and two sealed ball bearings. This planetary unit has six gear mesh points and three gear shafts that have no bearings in addition to the two main sealed bearings. Of course, the sealed ball bearings don't need lube, but the rest of the points do.

Frankly, I don't see why they would recommend two different types of grease. You might be able to find small quantities of PTFE grease at your local Wal-Mart. Look in the hunting/fishing section, as well as the automotive section. I think they sell little grease tubes for maintaining gun and fishing reel mechanisms, or outboard motors.