I have heard two theories:

1-Completely drain the radiator, then get under the car and remove the drain plug on the engine block and let it drain.

2-Then I have heard to leave the radiator drain plug open with engine running an warm, while continually adding water to the radiator.

I think the second would be much easier, but in your opinion, would it work as well?

 

I used a Prestone flush kit from Wally world that put a hose fitting in the water pump line. Did a flush and drain cycle several times it until it was all clear, then COMPLETELY drained (via block drains) and refilled with proper distilled water/coolant mix. I had previous issues with the Dexcool clumping and wanted to do it right. I'd rather do it the block drain way, just to make sure you get as much tap water/crap out of there as possible. That should help prevent future clogs or issues.

 

dont forget theres 2 block drain plugs, the knock sensor on the passenger side and the plug on the drivers side.