Feel free to post here or in the comments of the gist what issues you've encountered, maybe there's something we can improve. The guide is not perfect, I spotted multiple things that would require more precision already, but so far was too lazy to update it thoroughly. However I did multiple backups and restorations over the week-end and can confirm it works, you can even restore a backup from one Proš to another Proš if you rename the TWRP folder to match the name of the second Proš (using "fastboot devices" to get its name). It's possible that the issue you've encountered was with backing up the hybris-boot.img, and couldn't go further. There was a change in the permissions of this file over later updates and it couldn't be backed up the way it was initially written in the guide; that part has been updated now.