First time disassembling my 6s and both strips came off without breaking. Not sure if the idea for rolling the strips was in this guide or elsewhere, but I wrapped it around some tweezers for the first strip and then a small pencil (more symmetric) for the second strip…and pulled/rolled both rather slowly (never pulling past bottom of case). During the first go around with the tweezers, the strip started wrapping unevenly and it was pulling one side of the first strip more than the other. The sound the strip was making changed and it started becoming more difficult to remove, so I repositioned to a more symmetric part of the tweezers and it stopped being difficult. For the second strip with the small pencil, kept it slow and I didn’t have any issues. I think keeping equal force across the strip helps it not to tear, but I’m no expert.
Glad I read these comments about the screen cracking because I was really trying to force this thing open (with some heat applied already), but it wasn’t budging. Kept applying heat and light force and eventually it started coming apart. The suggestion for placing the pointed end of the spudger in the headphone jack while prying up worked for me and an extra set of hands would have been ideal.
In the end, with the spudger in the headphone jack, placed a guitar pick in between the screen and the backing and slid it along the bottom left. Left the tip of the guitar pick in to hold the gap and then was able to use the spudger to complete the process as shown.
Peeled off the first sheet, aligned, and then placed. I used one of the existing holes to make a cutout for the battery connector (since I had already inserted the battery when the other guide indicated the adhesive should be placed). Used two sets of tweezers gripping inside the holes to carefully align and place.