Take the car for a drive to warm the coolant with heater set to on. I drain coolant while it's warm. Fill with water and repeat. Much of the old coolant will still remain in block so this flush will help dilute it. You can undo the block drain to help that. Now you have to clean the crap left in. I use Prestone flush with water and take it for a drive to heat it and flush it through. Drain and fill with water, repeat the drive and drain to take out the flush chemical. Put in your anti freeze and top up with distilled water. While you can buy that I use water from my dehumidifier (I live on the wet coast[:)]).
I have a friend that used CLR (calcium, lime, rust remover) on his Toyota truck rad (removed all sorts of crap) and cured his cooling problems. While that may be good with rad out like he did, it probably isn't too good for our aluminum head so wouldn't use it in place.
I use this process on all my cars. My TR7 never over heats under any condition with standard fan.
TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra
