Hey bud, the backs can be an absolute mission to bleed.
Firstly remove the hose(from the master cylinder and caliper) and filler cap off the master cylinder, fill both sections full with fluid, hold your finger tight over the filler hole that the hose hooks up to, while pressing very tight push the brake lever up and down until the fluid pushes past the seal your finger is creating and you are unable to hold the pressure then fill both sections again(if there is no pressure, master cylinder is bad), now attach the hose and banjo bolt to the master cylinder and tighten but leave the filler cap off so you can fill the cylinder with fluid when it gets low, now holding the hose seal, the other end(caliper end) with your thumb and finger creating a tight seal, holding the hose below the master cylinder start pumping the brake lever and when depressing release the seal on the end of the hose with your finger slightly letting some air out but seal again before lever reaches bottom, and keep doing this until the pressure reaches a point you cannot hold it from pushing past your fingers, when this happens keep it sealed and hold the hose above the master cylinder, make sure the caliper is filled with fluid also(make sure the caliper is full of fluid where the hose attaches) still holding the hose above the master cylinder insert the banjo bolt and washers and then quickly attach the hose to the caliper, so it should all be back together.
Holding your thumb over the filler on the master cylinder start pumping your brakes up, after about ten presses on the lever loosen the nipple on the caliper and fluid should start running out of it if you did it right, do not pump the lever and let it gravity bleed, keep an eye on the filler as the fluid runs out filling it up(do not depress the lever at all while the nipple is loose), its a lot to take in but doing it in sections like this you know you have fluid in every part of the system, if it did not work try again.
