Just go to droid ultra, original android development. It's in the threads. You'll find many explanations.
Use pie exploit by jcase, and then to keep root after reboot you'll also need to use wpnomo.
I had a very hard time with wpnomo. Maybe due to our pcs. I just decided to unlock my bootloader on my 32gb droid maxx earlier in the year.
Dan Rosenberg just presented an exploit that will hopefully work it's way to us. So what I'm saying is, keep delaying update, try pie and wpnomo. If it's too difficult just wait for the bootloader because it's soooo much easier to modify with an unlocked bl.
Sent from my unlocked consumer edition Motorola Droid Maxx xt1080m.