Disc brakes feel spongy no matter how much I bleed them

I have not tried this yet but others have said to gravity bleed the front disks. open both front bleeders, and keep the rear ( larger) cylinder full as it drains to the disk bleeders. close the disc bleeders when no more bubbles come out. some clear hose on the bleeder is really helpful (can not do this on rears due to residual pressure valve.)

I have also found that by pressing the pedel down too fast during bleeding can almost aerate the fluid. it took me a week of bleeding to learn that lesson.

Good luck.