I've checked my '80 300 TD strainer/plug a couple of times; never found it very dirty. I prepared a plug with a golf ball wrapped in a rag inside a plastic bag, and quickly jammed it up against the hole after quickly removing the strainer, and propped it in place with wood blocks or a 12-ton jack. I only had a cup or so of fuel fall into the pan I had in place. With this method I don't care how much fuel is in the tank. Other methods sound good too.
Steve