Just completed the n52 coolant flush on my 06 330i (07/06 build). A few notes:
1. REMOVING BLUE DRAIN PLUG: Removing the blue plastic drain plug is not easy as its a very large flathead screw driver (which I didn't have). I used an old 5-in-1 painter's tool that had an ~ 1-1.5cm wide portion to turn the drain plug. Worked great (lots of solutions here).
2. Don't forget to remove the coolant reservoir cap when draining the radiator. When only about 1-2 oz of coolant drain out (and you commence freaking out as to why only so little drained/how your car didn't blow up w/so little coolant), you'll know b/c the cap is still on so a massive vacuum is preventing it from draining.
3. BLOWING TECHNIQUE: After draining the radiator (and squeezing the right side large radiator hose, as mentioned by OP), I used a small funnel that fit perfectly over the reservoir area and blew into it to flush extra coolant out (I got it to form a perfect seal by pressing down on it forcefully). I got quite a bit out, but nowhere near another poster's 95% claim. I know this b/c of point #4.
4. WATER PUMP HOSE DRAINING: After draining the radiator and blowing the coolant w/my lungs, I figured I might as well do this whole thing right and drain the water pump area too. I had to massage a small screw driver around the hose to loosen it's grip on the water pump. Then, I, w/2 screw drivers, worked one up into the hose, allowing coolant to start to drain. I held it there for ~5 min as coolant drained. I got A LOT of coolant out this way, even after draining the reservoir AND blowing the coolant (almost as much as the radiator drained). Therefore, I HIGHLY recommend you follow-through with this part of the procedure. It was a little tedious but once I got that screwdriver inside the U-shaped hose a little, coolant started flowing. Once it stopped, the hose came off real easy to allow the little left to drain.
For reference, here's the water pump hose referenced here and elsewhere:
