the system never went dry. Res = reservoir, we use that abbreviation in the 30 years as a aircraft engineer, guess it was too vague.
I completely understand “res” and its meaning. I have wrenched professionally on motorcycles for more than 40 years. I just retired recently.
Your original statements were incomplete and confusing.
By cracking open the banjo bolt, you have put air all the way down at the pump/piston itself now.
My recommendation is to:
1. Remove the caliper from the wheel.
2. Use string or a bungee and raise it as high as you possibly can ABOVE the height of the piston and fluid reservoir. Make height your friend as the air will rise to the highest point in the brake fluid line.
3. Place something solid, like a wedge or wrench, between the brake pads to prevent them crushing together.
4. Follow my instructions on the post I gave you the hyperlink to regarding 2 person bleeding.
One of you generate pressure by repeatedly pumping the piston then holding solid pressure while the other slowly cracks open the bleeding nipple with the long tube on it (sitting underneath a layer of clean brake fluid), and the piston/pedal slides smoothly and slowly. Close the bleeding nipple before the end of the pedal/piston stroke. Rebuild pressure and repeat again and again until all air has exited the clear tubing and only fluid is coming through.
Raising the caliper earlier will make air your friend as the air in the line will want to rise inside the fluid as you bleed out the line.
Do not let the reservoir run out of clean brake fluid while doing this.
Good luck!