Engine Coolant Replacement, Control Valve Position?

I need to replace the coolant control valve on my prius and I am changing the coolant while I am at it. I have read several threads regarding the coolant change but I have a couple questions that I couldn't find an answer for. First, I have techstream a no-spill funnel, and a venturi vacuum for my shop air compressor. I'm curious on the position of the coolant control valve, is it possible that it could be in such a position that would prevent coolant from entering either the heater core loop or the heat storage tank? How about applying vacuum to the system, would the electric pump or the valve impede the vacuum? I was wondering also if I could attach the vacuum to the bleeder port of the radiator(with the port open) to apply the vacuum rather than buying an Air Lift type setup. Your thoughts would be greatly appreciated.