The "simple debricking" short summary: Set fastboot mode with MfgTool (or diags), fastboot flash diags image that has SSH pre-installed, use diags SSH to "dd" main partition image to /dev/mmcblk0p1, set bootmode to main, and reboot.
MfgTool does not change the bootmode. It just forces a direct boot (even on kindles that cannot boot diags). Unplugging the kindle USB or resetting the USB port by rebooting the host PC drops the kindle out of fastboot mode. There is now a fastboot for windows so you can do it all from windows.
Or you can do it without MfgTool (or windows) IF you have diags access. Set fastboot mode (permanently until you change it with the fastboot tool) from diags (exit menu / install fastboot package). Then you can use any fastboot (windows / mac / linux).