Im just thinking outloud here, is there a way to disconnect a outlet tube and reattach your own short tube that drains into a bucket, then tape the stalk 'on' so the pump runs continuously and drains the reservoir.
Take a milk jug and place it on the wheel hub that's next to the hose that connects the hoses to the hood. Pop off that hose and place it into the milk jug and close the hood slightly so you can put up the windshield whipers. I used a basketball to hold the hood up just enough to clearly see the milk jug. Just hold the sprayer until the you empty it out. Now it's just a matter of putting new fluid in and reconnecting the hose”