Yeah when I did mine I drained the radiator and got what came out, out. Then I filled with Distilled water and started it up ran till the thermostat opened up, and repeated!! so I ran Distilled water Twice and drained!!!
As well I turned the heater on to be sure that flushed as well!!!
Some people miss that one!!! but there is a shut off valve to the heater core!!!

Finally I filled with straight red coolant since the water was already in the block, and I was comfortable with the flush!!
After filling the radiator with coolant and turning it on and running till it showed full completely I filled the reservoir with distilled water!! to the min line that is!!