Wanted to be prepared for battery replacement if/when needed.
I may have had a little edge on some folks with 38 years of electronics and computer hardware/software support worth of skill sets, but I was a little intimidated when getting started. Especially when the first Pentalobe Screwdriver did not seem to want to lock into the screw head snugly. The second Pentalobe Screwdriver seemed better suited, and got me through loosening all 4 screws of the two iPhones. Putting in the 4 replacement phillips screws was a cake-walk.
I was not aware of a guide for replacing the 5-Point Pentalobe Screws, but what worked for me, was:
1) Apply a little pressure toward the screw with the screwdriver while very slowly turning the screwdriver to search for locking/gripping in on the screw.
2) Once it feels as though it is locked/gripped in, very slightly test turning the screw to ensure maintaining the lock onto the screw head.
3) Once assured of the screw head grip, lessen slightly on the pressure toward the screw as you begin to back the screw out counterclockwise.
I was lucky to have had two liberation kits, because the above steps did not seem to work so well with the first screwdriver, whereas it worked great with the second one.
I later found a tip on iFixit where a contributor was talking about ever slightly grind/sand the very tip of the screwdriver. Perhaps that may have worked on my first screwdriver that was not gripping.