I have changed the coolant 3 times now, every 2 years, and drained the system via the factory supplied drain valve. Once the radiator cap is off, I got the system completely drained, every time. Remember the drain valve is located lower than the lowest part of the engine cooling system... So this should work. I have not seen any other drain cock on the cylinder block, only the nylon one on the coolant hose.
Hope this helps you Sixdogs.