While the car's on the ground, it's helpful to loosen the upper strut nut, though with the air impact, you can do this at pretty much any time. Note the form that's only for pictures - you'd break your silly wrist if you actually tried to operate tools like this.
Opening the bleeder valve is the correct way to retract the pads. You can force them back without opening the bleeder, but you'll force crud back into the braking system, where you don't want it. Opening the bleeder makes it very easy to just push the pistons back and get the brake pads past the inevitable ridge on the rotor.
With the pads retracted and mounting bolts removed, the calipers come right off. Secure them out of the way without stressing the brake hoses (i.e. don't follow what we're doing in the picture). We used a creative arrangement of bungee cords to hold the calipers out of the way.