Hey first post here but I would also recommend that you take off / loosen the cap on your brake fluid reservoir while pushing back in the pistons. When you push in the pistons that fluid is getting pushed back into the system and that can build up pressure and pop off the cap on your reservoir, which is why you want to take it off. Like daschwa said bleed the brakes too. Get a bleeder kit and a small bottle of brake fluid while you’re at the store picking up your brakes.