If I was doing this job myself, I would rather drain the engine block & heater core properly. Flushing the system with distilled water would still leave an unknown quantity of water in the engine block. Since most coolants come already mixed with water, I would rather drain the radiator, radiator reservoir, engine block, & heater core before adding the new coolant.
If someone is doing their own coolant changes at the recommended intervals, I think the procedure shared down below is more beneficial than flushing the system with distilled water.
Mohammad or someone showing this done on a Mirage would be nice some day.
If the cooling system has been neglected, flushing with distilled water & coolant flushing solution may be the better approach.
If I did this second method, I don't think I would skip draining the engine block. There's no way of having an exact mix of coolant if you skip that step.
I only share all this, because some on this thread have said, they would skip draining their engine block. In my opinion, draining the engine block coolant is easier than the flushing system.
If someone suspects they are having cooling issues, I would do both (flush the system & drain the engine block before adding new coolant).