Done it before on my old s3 by adding a couple of crushed up dishwasher tablets to the water, letting it idle for ten mins after reaching max temo and then draining through lower rad hose, repeated this a few times untill water was looking fairly clear and then flush through with clean water.

The whole thing was a bit of a ball ache to be honest and im just wondering if there was an easier way of doing it?

Cheers