And, before you push the piston back, open the bleeder valve on the caliper. This will prevent contaminants in the fluid from your caliper and flex-hose from being pushed backward into your finely valved, needs to be kept very clean, master cylinder. A lot of master cylinders are ruined this way.
If you like, run a small vinyl hose from the bleeder to a container to catch the old fluid. Close the bleeder screw before you let go of the c-clamp to prevent air from being sucked into the caliper.
Take a few extra minutes to save yourself the time and expense of otherwise unnecessary repairs.