The Project Pad

Im trying to bleed my brakes on my CQ, not much luck

The whole system was totally dry for year. Front Porsche 993 Turbo calipers, urS4/6 rear calipers. Calipers had some fluid inside them.
I made the poor man pressure bleeder and could bleed the front brakes with it on the s4 right away

The order: Right rear calliper; Left rear calliper; Right front calliper; Left front calliper
Endless bubbles are coming from the right rear caliper, i let 2L fluid through, they are still coming

Last night ive read that i should bleed the brake master cylinder and proportioning valve first.
How do i bleed the brake master cylinder?

I did bleed the proportioning valve, no bubbles at all.
What should I check? What im doing wrong?

Thank you
Chris

There's a nipple on the master cylinder in one of the rear ports of I'm not mistaken. Fronts are split circuit, and rear is just one line going to both rears via proportioning valve

Item 3, item 7 and then the calipers, rear right, left, front right, left.