Actually, there is not a high need to overly cool the recovery tank if it is large enough. A slow trickle of cool water from a garden hose is good enough. If you don't have running water nearby, an ice water bath will help. The only time cold temperatures are really needed is when you are trying to recover without a suction source. Given enough time, a cold, empty tank will literally suck all the liquid out of a sealed system. The refrigerant remaining in the system will be at whatever pt the tank is in equilibrium with. If the tank temp is below condensing temp,and the tank is not full, then all the liquid will be in the tank. The gas remaining in the rest of the system is a trivial fraction of the total mass.
The taps for low and high pressure can and should be placed close to the cap tube/metering device in the recovery a/c unit. This allows the incoming refrigerant the maximum distance to expand or "burp" on its way into the compressor. On the discharge side, having the extraction valve at the other end of the condenser coil allows it to condense and subcool. As long as your recovery tank is below the condensing temperature of the high-pressure refrigerant, it has no choice but to stay a liquid once it goes in the tank. Once the recovery tank fills up sufficiently (2/3 to 3/4 of the way full), swap it out for an empty tank and slowly fill the tank until the pressures equalize.
The donor unit should not be running during the recovery process. The window shaker doesn't need to be force-fed, nor the donor compressor starved. That being said, if you feel confident about it, the donor unit can probably pump down its own a-coil and have its service valves closed before recovery is done.
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