Well seeing I am pure lazy I just buy a flushing tee, (if I just got the vehicle), and some draino. Let the vehicle warm up with the old draino in then let them cool. Drain it then flush the system with the tee for awhile then refill. Works like a champ.
Sure cleans up alot of scale and rust in a hurry.
I'll add yes I amprepared to replace any parts that may be screwed up in the process but to date that hasn't happened. Not saying it good method or bad just mine.
When I changed mine I put in Transport coolant, the mechanic at my dads work said it has cleaning agents in it and it will last much longer then normal "car" coolant. its really Dark green even mixed its really dark