I don't roast, grill, or fry mine so I can't help you with that. There are three different possible "treatments" for the meat.
Aging is where you let rigor mortis pass. If you cook them fast enough after butchering rigor mortis doesn't set up. How long that takes sort of depends on the temperature but it doesn't take real long. How long it can take to pass can vary too so I'm not going to give you a time. But if you try to wiggle a leg and it feels at all stiff, wait some more. You need to keep the meat below 50 degrees Fahrenheit to keep bacteria from growing. That could be in your refrigerator or maybe a chest of ice water. Butcher and clean it before aging. It's easier and it cools off faster.
Brining is where you soak it in a salty mixture. The meat you buy at the grocery store is probably brined. The salt adds some flavor, though you can do that when you are cooking it if you wish. The main thing brining does is that it causes the meat to hold moisture. If you are going to cook it with a wet method, like a crock pot, pressure cooker, or soup, it's not very important. But if you are going to grill, fry, or roast it can help a lot.
Marinading is where the meat is soaked in an acidic solution, often wine or vinegar. Like all the other steps this can add flavor, depending in what you put in the marinade, but the main purpose is to tenderize the meat. The acid breaks down the fiber to make it more tender. The stronger the marinade and the longer it is marinaded the more the fiber breaks down. If you marinade a young bird too long it can turn mushy. But a proper marinade in wine is a key part of how the French turn a tough old rooster into a tender tasty Coq au Vin. With the French you know it has to involve wine.
When Mom made chicken and dumplings with an old hen she did not do any of this. She'd tell me to get one. I'd pluck and gut one and give it to her. She did not age, brine or marinade it, she cooked it immediately. That was real comfort food.
For your methods, I'd suggest aging it until rigor has passed in a fairly weak brining solution. If you marinade it, say with barbecue sauce, don't overdo it as far as timing goes. It may take you a bit of trial and error to get it where you want it, but you can do that.