Oh god… been trying to bleed front brakes today with no success… so new brake cylinder kit, new brake lines, new pistons, seals and pads… 2 hours and nothing. 
Reverse bleed it…I use a syringe and pump the brake fluid into the caliper bleed nipple, one side at a time…air doesn’t normally like going down and tends to sit in the highest point in the system.
You’ll never get a good “rear brake pedal”…just the way they are I guess, still works but feel is terrible.
Smithy.
Ok cool… I’ll purchase one tomorrow and give it ago… again thanks 
Are you trying to bleed both at same time?
Pick up a Mighty Vac pump. When you use it, you’ll probably need a bit of Teflon tape on the bleed nipples so you build a vaccum and don’t have spiral leakage at the threads
Okay, thanks for the advice 
Reverse brake bleeding using a syringe worked a treat 
Result…an old trick taught to my by my father…many moons ago.
Smithy.