each time I have had occasion to open and partially drain the brake hydraulics on my series 2 I have had to pressure bleed the fronts to get them done -- otherwise my wife could pump the pedal all day with no result.
I use a simple set-up -- an air line into a substitute cap using 1/4" irrigation hose and a double-barbed irrigation fitting. all stuff I had lying around though it could be cobbled together many other ways:
this approach just applies modest air pressure [15 lbs or less] to the top of the appropriate reservoir, hence it does not actually contact brake fluid, it doesn't even have to be perfectly air tight.
any old cap may do -- that one was for a lawn mower gas tank, the one for the clutch was a plastic top from a spice bottle I found in the pantry. I made some rubber washers from an inner tube to help it seal better. for an air supply I used a portable tank with just 15 lbs in it --- but almost any small air supply could probably be made to work [spare tire, 12vdc compressor, garden sprayer, etc].
all it has ever taken me is a brief shot of air to bleed each front wheel - I suppose just enough to overcome the m/c system. I finish with the usual pump bleed but perhaps that is not really necessary.