Cleaning out water jackets, with block outside car.

Power washer through each hole with the freeze plugs out and water pump off the engine.

You'd be surprised at the pile of sand that will come out. A lot of the sand has been there since the engine was first cast.
Yeah i know that’s what I did and man was it nasty, I wanted to see if I could fill it up and leave some chemical in it over night to help clean out what’s left on the walls