Just broke my screen with this guide and the ifixit repair kit. I found a couple parts misleading:

The screen adhesive is very weak and you should not need to re-apply heat.

In my experience, the screen adhesive was not weak at all. It was so strong that I had trouble getting a pick under the screen. I sanded down one of the picks to make it thinner and finally got it under the screen, but when I was cutting the adhesive the screen broke because the adhesive was still so strong. This was after heating and re-heating the iOpener multiple times.

With the pick 1 mm into the gap, pivot the pick upwards to a steep angle.

The end of the pick you hold should be upwards, as in the picture, but the part of the pick in the phone should actually be pointing downwards, otherwise it will slip between the OLED and the glass of the screen.

Good luck, this isn't easy.