Bleeding master cylinder

If you have some old brake line hanging around disconnect the lines to the cylinders and cut two pieces of brake line, and attach them where the other lines go. Bend the cut ends into the reservoirs and fill it up. Just like bleeding anything else keep pumping away until you don't see any bubbles.
I was hoping do do just this as I have plenty of brake line about but I cant locate the right thread unions to fit the master cyl over here as European ones are much smaller, I think I need 9/16.