If the brake is tight, it may be very difficult to release the cable - just can't get much free cable by holding the brake pads against the rim. If your barrel adjusters are screwed out, you can screw them in to get more free cable. It's also possible that the narrow opening in the cable hanger is too tight for your cable to pass through easily. If that seems to be the case, just widen it a bit with a screwdriver.