To bleed via the banjo bolt, do as someone commented:
"loosen the banjo bolt just enough so that fluid and air could be expelled when the lever was pulled then tighten the banjo a little before releasing the lever. Then pump the lever a couple of times. Repeat this process till pressure is felt at the lever. It works and is a lot easier than it sounds."
"Sometimes the air locks in the top half (of the caliper). I used to put the whole wheel assembly on its side (with the caliper facing up), and then bleed it to finish by lightly loosening the banjo then tighten till it had pressure just to get rid of the last few air bubbles." "Imagine where the air gets trapped and jiggle it round, allowing it upward."
Before fitting push the piston out as far as possible, stopping before the seal is exposed. Keep it horizontal and fill it with fluid. Now atttach hose and tighten banjo bolt.
If you now squeeze the piston in it will force the fluid through the pipe, pushing the air before it. Worked every time on my 80's Chiselspeed conversion. You must remember to keep the unit on its side so the air at the top is where the banjo bolt is.