Cleaning out water jackets, with block outside car.

Hey guys wanted to know what I could use to clean out my water jackets in my block, I already have flushed out all the gunk and rust sludge,

I wanted to put some new freeze plugs and leave the plug at the highest point on the back of the block open and run some CLR in the blocks water jackets and let it sit for a couple days and flush it out again. The reason is I don’t want to disassemble my engine which has low miles and is a runner, just want to give it a good flush!

Would CLR work?

The heads are already off and they will get hot tanked after the porting is done.