Ensure car heater is on hot (not fan, this ensures that the water in the heater coil is exchanged over aswell)
Remove radiator cap (vaccum will slow the drain considerably)
At bottom of radiator theres a plug, unscrew and drain water from radiator, hoses, and head.
Underneath exhaust manifold, at bottom of block theres also a plug, unscrew and drain water from block.
Pull radiator out, flip upside down and flush with garden hose, drain and refit and plug
Flush block with garden hose, drain, refit plug
Fill cooling system with premix inhibitor, or mix concentrate solution with demineralised water
Fit radiator cap, ensure overflow bottle is full, start car until warm
At the top of the plenum theres a radiator drain plug (You can also use temp sender). Remove and wait until water starts pouring out and refit.
Stop car, top up overflow bottle and radiator if needed.