I did flush yesterday. First drained out the old coolant through the petcock(can not reach engine drain plugs), then disconnect upper and lower radiator hose, use garden hose flush radiator by water come in upper hose come out lower hose. Install a Tee on by pass hose, remove thermostat, reconnect upper hose, let water come in the Tee, come out lower hose, use two clamps(one clamp on bypass hose, another one clamp on just after coolant temperature sensor) and to force water go through this order, heater core, water pump, engine block, radiator. Last remove coolant expansion tank to clean up. The result is good.