I used my homemade fuel line air-tank adapter...lol...just a beverage line with a tire valve stem clamped to it, and clamped to the main fuel bulkhead connector. I then capped the fuel tank vent with one of the cleco rubber caps and screwed on the fuel drain valve, finally screwing on the fuel tank cap throat and cap.
I then hooked my air tank pig and pushed some air pressure into the tank, I carefully watched it expand some to ensure it was pressurized, then squirted soapy water on all joints and connections. The only place I initially got bubbles around my fuel cap, so i tighted it up by turning the nut on the bottom. Then the only place I saw bubbles (a few) was through the tank cap key hole. Nothing really I can do aboiut that and i felt that it's tiny enough that it's probalby not much of an issue anyhow.