you might be doing it right, take off the expansion tank cap and see if it is flowing. You will see coolant pissing in the tank from where the small hose attaches to the top near the cap.
make sure the car is not hot when you take the cap off (obviously).
if it works, put the cap on and let it finish the vent cycle.
2006 330i - Jet Black - 19" E46 M3 wheels - HR Sport - 206,000 Miles...