Coolant Dam or not?

[sonyg]

I got a 2350 isx in a 2016 KW T680. I was going to change the dossier valve and the service manual says to use a coolant dam device which appears to be a air operated vacuum / pressure tester that will stop the coolant from draining out the engine block when you unscrew hoses to the valve. My radiator also has a warning sign saying not to drain coolant. Question is do I need this device or should I just try to change it without losing a lot of fluid? I know the video rawze made said they drained the coolant but didn’t know if that was ok with this system per the warning label. Thanks