[Deezelweazel]

Bleed valve?
Are you talking about the one with the plug close to the fuel rail? Never used that one.
Maybe you get a small manual lift pump like the ones Bosch sold in the past.
With that one you can very conveniently purge the fuel filter if you open the drain on the fuel filter. It has a small anti drainback valve installed in the pump. Once the fuel is in the filter it will remain there.

Another cause for the constant drain could be a missing fuel line in the fuel tank. The feeding and the return line must reach to the bottom of the tank. If the return line is missing, it will drain the line automaticallly.