This is the tutorial I used to learn. Older birds need to be slow cooked at low temps. The older the bird, the tougher but more flavorful the meat gets. I prefer just to make stock but I process my own meaties as well.
The easiest way that I have found to process old layers is to completely skin the chicken leaving the meat. I would then tenderize the meat and marinate it for a day or two before cooking it in the crock pot. I've also had some really good chicken that was breasted out and baked in the oven using some pancake batter and seasonings.
There are so many different ways you can process a chicken I can’t come close to coming up with what is best for you. To me that’s tied into how you use them, whole or cut into pieces, as well as lots of other things. To me you need a sharp knife and plenty of water. A pair of poultry shears are very useful and helps keep your knife sharp.
Personally I skin older hens. It takes some physical strength and there is a learning curve, but my wife wants them skinless anyway. Older hens have some connective tissue holding the skin on but are nothing like older roosters. Those are a pain to skin. If the hen is molting, skinning takes care of the pin feather issue. If a chicken is molting and you try plucking you have a mess to deal with. But some people like the skin on.
I cut mine into serving pieces as I butcher, which makes me kind of slow. I also save parts that are not serving pieces to make broth. Some people like to cook the entire carcass.
You can eat any chicken of any age and any sex but those things affect how you can cook them. As someone mentioned, the older they are the slower and moister you need to cook them. For older chickens, Coq au Vin, stew, or chicken and dumplings are traditional ways to cook them. Crock pots and pressure cookers can be used. Never boil, just a gentle simmer. As others said, they make great broth. My current preferred way to cook an older hen is to cut her into serving pieces, rinse her off but do not dry, coat with herbs (I use basil and oregano), then bake in a fairly tight covered baking pan for maybe 3 hours at 250 degrees. That’s not a typo, 250 degrees. Slow and moist. Many people like to brine or age their chicken in the refrigerator but I don’t. I made broth overnight with non-serving pieces.
There are so many different ways to do any of this and we all have our own opinions I can’t come up with any way that’s best. There are a lot of great ways to do these things.