Well here’s my spin on piston removal. I have done the grease and air many times before I came up with a better mouse trap. It is true, necessity is the mother of invention. Although I’m sure I did not invent this approach, it felt like I did at the time. There had to be a faster, easier safer away. The big problem with air and grease it is difficult to get both pistons out without a frustrating effort. Air will not get the tough pistons out. And air and grease cannot be easily applied to both pistons.
Here’s my process. Separate the calibers, drill a hole through the center of each piston and tap it with either a 1/4 inch or 5/16 inch tap. Pound the piston in to brake (pun intended) it loose then screw in a bolt and it comes right out. It takes less time this way than cleaning up the grease and dealing with “the other“ piston to get out. I never found a piston that would not come out this way. Actually, I came up with the idea when I couldn’t get one out with air or grease.