I tried to flash Android 4.1.2 to my GNex using this guide. I downloaded all the necessary files and unzipped them to my home directory. Then I opened Terminal and changed directory to where the fastboot-mac files were.
asked Jan 23 '13 at 12:37
Flash everything JB related. Follow all the steps, to the letter. Make sure you double-check everything. Find multiple guides, check XDA, check wikis. You want as much correlation as possible.
Yes, you should flash the JB bootloader. You should flash everything the system.img, the cache.img, even the userdata.img. If you want to install custom recoveries and etc, you should do it after you get a fully functioning build on the device.
answered Jan 23 '13 at 15:58