nope..the trick is to top up the radiator reservoir, with engine running, bleed screw loosened, till the green oozze has had its way... cut the engine...go watch a movie and grab dinner...
return to car, engine's now cold, top up to the line indicated in the reservoir tank...
what u've done, is to release the air from the system, and when filled up to the "KALT" line indicated on the reservoir, the water levels would be enough by bmw's recommended levels...
usually i throw in half a bottle of Purple Ice to help the 50/50 mix...
and i only use bmw's coolant..
.. not exp, like $6.50 a bottle or something...my humble 4-potter uses 2 bottles of coolant with 2 bottles of water in a 50/50 mix for a complete flush..