Brakes/Rotors

First time changing brakes and rotors (2016 Nissan frontier). I’ve been hearing a squeak noise from my rear brakes, I know it’s a warning sign of the pads getting low. I’ve read some post about opening up the bleeder screw on the caliper when pushing the piston back in, or some people have said just remove the reservoir cap before pushing the piston back in. So which is it? Loosen up the bleeder screw or just removing the cap.