I've got about 70 birds under my belt and have given this a bit of study, a master by no means, but I can pass on what I've learned.
after an animal is butchered, rigger sets in, which causes the muscles to tense up. it takes at least 4 hours of "resting" to get this to begin to release. the resting can happen after freezing, if you are in a hurry, you just have to remember to do it or you end up with rubber bands in your teeth. the key after butchering is not quickly freezing but quickly chilling into the 30's f. once chilled, the bird can go for days, some say a week or more in the fridge. in my book, the key to safety is assuming that every bird carries something that can make you sick and to take measures to protect yourself, mainly not shying away from bleach spray for food surfaces and cooking it till it's well done but still juicy and tender, which is a bit of an art if you ask me. the most tender chicken I have found a brined chicken that is then "lemon" baked. there are lots of great brining recipes out there, you can be exact or you can just wing it, about 1/3 cup salt and 1/3 cup sugar and all the spices and herbs, a carrot, maybe a potatoe chopped up, an onion diced and then add enough water to cover the chicken, making sure the salt and sugar dissolve. you can leave it in the fridge covered for between 12 and 72 hours. you can strain out the spices and veggies and bake the chicken with them but they will not be worth eating, but will impart flavor and aroma. play with it, you will find the concentration and duration that meets your taste. as for the lemon part, Lemon looses it's flavor when cooked but you use it for it's chemistry, not it's taste per say. I boil a whole lemon for 5 minutes just before I'm ready to put the bird in the oven and then use a spoon to get the lemon out of the boiling water and ass I place it into the cavity I pierce it with holes using a small pairing knife. You'll notice the lemon juice squirting out and it continues to do that as it cooks, releasing moisture and ascorbic acid. the acid helps tenderize the meat. You can then spice to taste with whatever you like. if you want lemon flavor, squeeze a fresh lemon over the carved meat at the end before serving (the cooked lemon will be spent and should be discarded with the carcus). I cook for between 1.5 and 2 hours depending on the bird, usually 2 hours at 350 f. I use a convection oven so I have to use a lid to keep it from drying out. I leave the lid slightly open to let some moisture out, you will find what works best for you and your oven. long slow cooking tenderizes the meat and I think it's the best way to enjoy birds that are on the tougher side.