I see, I usually use gloves and I heat the butter so it is super soft enough to easily mix in the sage that I add to the butter & it melts under the skin as it cooks. Gloves help avoid the ickiness factor so there is more patience while I work with it.
I also put fruit veggies and spices inside that I discard after, I think these keep the inside from drying out and make it smell nice. In general, this is a collection of fresh bits I used in other dishes the day before and day of like apple core, orange peel, celery leaves and the base, outer onion skins & the top and bottom, plus thyme, rosemary, sage and such - anything fruity or veggie works. I don't stuff with stuffing for food safety reasons but this collection of bits does the job without risking food poisoning or anything.
Also, there is a whole thing about old hens and young toms being tough and stringy, so probably bigger hens and smaller toms are less desirable.