2002 Sable: Heater Core & Flush

My 2002 sable's heating system isn't throwing heat... we narrowed down the problem to a dirty heater core and I'd like to do a reverse flush on it. How do I do it on one of these cars? :runaround:

Remove both heater hoses and leave open and use a water hose and stick a nozzle in one hose. Turn the water slow until you get flow and flush it out. If plugged you can over pressure the core so start slow until you get flow.