I’ve disassembled a sticky parking brake before but could not remember the trick.

Did a search an found this: https://www.stangnet.com/mustang-for...-brake.835751/

«*11) Then came time to remove the screw that the piston rides up and down on. At first I couldn't for the life of me figure out what was keeping it in there and I couldn't yet remove the lever mechanism from the back of the caliper (it was obvious the two were "tied" together some how but I couldn't see what was holding them). Finally I got tired of messing with it and just grabbed it with a set of pliers (with a rag on the end as to not scratch the screw) and sure enough it just popped out. It's got a little O-ring around the base of it that keeps it kind of suctioned into a hole (see pics for a clearer idea of what I am talking about). The screw also has a little swivel rod (don't know what else to call it) that just pulls out of the back of it. The other end of the swivel rod sticks into a hole in the parking brake lever (hence keeping it from being pulled out before).*»