Drain the system using high volume low pressure air, fill system with prep fluid, run engine to temp and drain all that with low pressure air, all sans thermostat. Replace thermostat and fill to capacity with Evans and purge all air as required.
Yes, full volume of Prep. I got four gallons of each Prep and Coolant. There are videos on the Webz to further explain.

 

I'm about to start my cross country drive - with the XF Sportbrake this year and not the xk, sadly. BUT GOOD TO KNOW I'LL GET TO TEST OUT THE AWD!

 

Why do you replace thermostat? If there is no pressure shouldn't it be removed?

 

You misunderstand or I phrased poorly... You remove the thermostat to enable evacuating all the coolant (also all the prep fluid when that is removed) to ensure that as much as possible is gone, without a closed thermostat blocking the pathways. Once all the Prep Fluid is pushed out, then the original thermostat can be reinstalled to operate as normal.
Removing the thermostat just removes the "closed valve" in the coolant passages to aid in full evacuation of undesired fluids.

 

Got it. Thanks.

 

Am sort of joking, but when you mention evacuating the system...visions of me duct-taping my shop vac to the thermostat orifice comes to mind. I can set it to draw or push ... 5hp of high-volume air.

 

Yep, that's exactly what I'm going to do. I have a pressure gauge I'm going to install and make a relief opening so I can keep the system pressure under ten PSI so nothing explodes. Once all (most) of the liquid is drained, I'm going to let it sit while on to dry out everything inside that WILL dry out. Water is bad for Evans, only 3% of total system volume of water is allowed before bad things happen.