Fuel-lubed all the fuel tank fittings and installed them then proceeded to pour a few gallons of water in to clean out the tanks and to check for leaks. I propped the tank up so that the "business end" (feed line, return line, and fuel sender end) was lower than the other end and let it sit for 10 hours. No leaks and no "stuff" in the tank.
Fuel tank propped up on a chair with water inside.