I can confirm that this method worked on my black K4 (using a Lenovo laptop normally running Win7 64).
My kindle was not bricked, so there was nothing to fix, only wanted a clean installation after playing around with it. The most tricky thing was getting it in USB download mode (thick fingers...). The instructions are very clear and easy.
Afterwards I had to reinstall the kindlet-jb to get KUAL working again (guess that is normal).
Thanks, appreciate all your effort!