Ok quick step guide, well this is how I did it.
Lid off coolant.
Take clip of bottom radiator hose, let run out.
Undue bleed screw, more coolant will then come out of radiator hose.
Flush out with water.
Put hose back on.
Fill up with coolant till it comes out of the bleed screw as a steady stream, do that up, fill coolant to max line.
Start engine, keep it at 3000rpm to get the thermostat to open, usually 10 mins.
When the thermostat opens the coolant will drop super fast, just keep topping it up.
For some reason though it always suddenly fills the coolant bottle back up and bubbles over, you'll see lol.