Yeah, I’m a believer in the crock pot for older birds but I’m sure people have good recipes for a pressure cooker or maybe even just a stew pot. You might look up Coq Au Vin, or Cock in Wine. That’s the traditional French recipe for an old rooster. Just be sure you are using a traditional recipe. A lot of the recipes you find on the internet assume you are using one of those 8 week old store bought birds. Totally different than an old rooster. Like Hummingbird said, the secret is low temperature, long time, and keep it moist.
The way I’d cook a bird that old I’d butcher it and cut it into the regular pieces; breasts, wishbone, thighs, drumsticks, and wings. I’d also save the neck, back, gizzard, and heart. I use the feet too but understand that would turn some people off. If you scald them you can twist the toenails off and peel the skin off which gets it clean enough for me but I can certainly understand the YUK! factor is hard for some people to overcome.
In a crock pot put a bay leaf and maybe 10 to 12 peppercorns. Cut up on onion, a carrot and celery stalk. Big chunks are fine. You’re just after flavor. Then add whatever herbs you want, maybe oregano, basil, thyme, parsley, and maybe a clove or two of garlic. Add the chicken and cover that with water as full as the crock pot can handle. Depending on the size of the crock pot you might have to make two batches, especially with that big old rooster. Cook it on low overnight. Nine hours is enough, twelve hours is not too much. You can try eating the thighs, drumsticks, breasts and wishbone but the meat might fall off the bone.
You can pick through the chicken and get the meat off all the pieces plus get all that’s just floating around. Be careful of small bones. Talk about good stuff on pasta, in a chicken salad, or on a taco. You’re not finished.
Save the liquid and strain it through maybe 4 to 6 layers of cheesecloth, then take the fat off the top. You have the best chicken broth you have ever tasted.