How do you flush your heater core?

Disconnect both heater hoses from the heater core or the engine, whichever is easier. Fabricate fittings to attach a garden hose to one of the heater connections. I direct the other heater connection into a bucket. Turn on the garden hose gradually until all the way open. Flush for 30 seconds. Reverse heater connections and back flush another 30 seconds. Reinstall heater hoses, top off radiator coolant reservoir. Done.