To level the Werewolf skill line you need to do kills while in Werewolf form. Each kill gives 5 points regardless if it is VR12 mob at Craglorn or Level 5 mob at Khenarthi roost.

So the task was to kill as much as possible during the limited amount of time given by the ultimate. While VR12 char.

After a bit of experimentation the plan was formed. And went from VR 1.5 to VR10 in 3 hours.

What you need is 1 SP if you want to speed up the process, so you can get the devour passive, which triples the duration of the WW form timeout if you feed at correct intervals.

1. Kill VR1 mobs. Preferably the ghosts at Stonefalls area, and especially if you are member of the fighters guild. You will charge ultimate pretty quickly.
   
2. Go to Auridon. Either Quendeluun or at North beacon, if you have Devour. If not, use the Ezduiin ruins. The mobs are packed on those area, with fast respawns.
   (I did Quendeluun since is close to the Quendeluun Wayshrine)
   Also all these mobs can be killed with a single heavy attack.
   
   Quendellun how I did it.
   
3. Get to the main area. Transform and start killing. I always did a clockwise run from the ruins near the entrance to Wansalen all way to the sea.
   Rinse and repeat. At the start is gives 1 to 1 1/2 levels per run until Level 7. Afterwards just bit less than a whole level per run.
   
   Please note. If you have devour passive do not feed on the first two Elves/kills, but on the third on the next spawn. It will charge half bar the first devouring.
   Then every four kills, feed and run. (preferably use a green stamina food to sprint)

Doing the above on Friday night I got to WW from 1 to 10 in just 3 hours. To kill the ghosts fast, used Camouflage Hunter and bow heavy attacks. You barely have to move, and almost all of them die on single Heavy attack from Stealth.

Hope I helped a bit. And saved you from the big grind that feels initially, the leveling of the Werewolves.