RedY2KS2k

When you blow the piston out of the caliper, you want a piece of wood where the brake pads should be so that the piston doesn't get damaged. Piston flies out, hits wood which is softer than piston, nobody gets hurt and nothing gets damaged.

The ideal way to clean up the "cylinder" in the caliper is with a "flex hone." Here's an example.

http://www.brushresearch.com/brushes.php?c1=1