Replace coolant

[even_u]

I've had issues with the coolant for years. Tried various types, but all water based coolant are causing corrosion in the system.
I rebuilt and replaced the internals of the radiator a couple of years ago, but the corrosion is still there.

Now I'm gonna use Evans coolant which is waterless.

Question - how do I drain all of the old coolant out of the engine block?
The drain plugs are set so tight that I'm worried I'll damage the threads if I unscrew them.

Will I get all the fluid out by removing the freeze plugs?