If you have read at least the first post of geekmasters tread here and understood:
and you have access via usbnetwork / ssh to your kindle you can probably follow ixtabs description here:
To do this, you need to have the files from here (in geekmasters post, reference links)):
Kindle "Forensic" Images (be sure to use matching partition and kernel versions):
Download URLs are here (this URL can change): http://pastebin.com/Wdw4L7yT
mmcblk0p2_ssh.img has to be in mnt/us/ to start with as well as mmcblk0p1.img for flashing to 5.0
For the kernel flash, the img is in the forensic link as well. I needed this for unbricking a 5.1 firmware, not from my 5.0.4, assume this is not necessary as long as you are on a 5.0.x firmware.
As mentioned, Geekmasters procedure worked twice for me! THX from my side again.