Hi,
I drain the tank, run the engine DRY to make certain there is no fuel in the crankcase, use a short length of ALUMINUM tubing to couple the feed line and the pressure line together, then use a few squirts of Air-Tool oil in the carb. Flip the prop a few times and put a paper towel plug into the Carb opening and another paper plug in the Exhaust. I then CLEAN my models with 409 Spray. My Van is clean and there are No Drips from the exhaust port.

WHY ALUMINUM Tube ? Check your old fuel tanks that have Brass tubes, if there is any fuel inside the tank, it turns GREEN from the brass pick up clunk and the brass tubes. I still use the brass Clunk, but all tubes are aluminum and I always DRAIN the fuel back through a filter into my fuel jug.
Ken