Just realised, while I posted this on Telegram and updated the wiki, it was never mentioned here. Oops…
I wrote a small app to make flashing the Teensy super-easy, no need for Arduino IDE, TeensyDuino, anything - it’s all self-contained in one simple program. Details on the wiki here but it’s as simple as download, unzip, Refresh list, pick the firmware, program !
If you find any issues, please let me know, either tag me here or log an Issue on github. Thanks!