Two things that I have done to get the air out and pedal firm.
Surge bleed the brakes - takes 2 people and the m/cyl(s) need to be fairly new. Open a bleeder and JAM the brake pedal to the floor. Hold the pedal down till the bleeder is tightened. Repeat as needed. Keep the m/cyl(s) full and do not use a mity vac or pressure bleeder to do this.
Caliper seals that retract the pistons too far can be "persuaded" to comply by removing the loose pads (one at a time!) and gently pushing down the brake pedal till the piston(s) move toward the rotor. You may have to gently hold the first piston from moving too far in order to get the second one to move. Reinstall the pad without moving the pistons back too far. Pad should drag on the rotor. Repeat with any loose pads.
JMR