You only use the wash out when the tank is EMPTY,
First you dump, then you rinse. Why would you "Wash out" a full tank?
Page 2: ONLY connect to that port (inlet) when you want to rinse the tank, when done disconnect, QUICK disconnects, are just fine here,, I put a short (like 10 inch) hose on mine, just enough so that the QD is outside the bay when the door is open, That way I can quickly hook up and unhook.
You can get Quick Disocnnects in the garden hose isle at hardware and Lawn and Garden departments in many stores. Too many to list.