Before you do any reverse flushing, drain the coolant, fill with plain water and drive it around with the heater on for a while. drain, refill with plain water +Nulon radiator cleaner, drive, drain, refill with plain water, drive, drain, then reverse flush the radiator, then add your long life coolant. (Don't get the engine to hot, as you are adding cold water to it)
Long and slow, but oh so clean.
Don't forget the coolant is poisonous to cats, so leave some out where they can get some :)
"I married Miss Right. I just didn't know her first name was Always."