How do you bleed the brakes on this vehicle please? on 1997 GMC Suburban 1500

Cannot get all the air out of the system, suspect a faulty ABS unit. Have a permanently soft pedal. After running about 15-20 miles rear brakes start to bind.

Asked by for the 1997 GMC Suburban 1500
You need a scanner to clear the ABS module after you bleed brakes on this truck or just about anyl modern GM truck. Is the Master Cylinder in good shape?