As the title suggests, hunter brew seems to have effect even for a character that has never prepared it. Animals avoid my PC (Ashlen Desmarais) and she can rest in the wilderness without a fire (still needs food and bedroll, however).
I am not sure if this is a bug or not, but... I can tell that animals running away from you is not reliant on having specific class or ability.
There are other factors where animal ai may try to avoid those they might fear or see to be intimidating. And that goes for any character.
I've played two RSDs, one with excellent physical stats and charisma, one without. The one without was often picked on by animals, but the one with great stats was not. I'm not sure how the animal aggro is calculated on the back end but it seems to me like animals know if you're tough and will steer clear of fights that they can't easily win. Just like in nature!
Starting next reset, RSDs will need to prepare the Hunter brew to get their free wilderness resting and animal avoidance.