Opening a folder while someone is kicking your ass is hard. In the early days of my current dojo, it was just me and the instructor for over a year. We did a lot of edged weapons work, and one of the games was: he starts working me over, and only stops when my knife is open. I could fill a thread with pics of the bruises. It was way harder from support side, at least at first. Waved folders worked much better for me. The OTF is the next thing I want to try. But fixed blades FTW, of course.