I put game animals on ice/water/salt/acv for at least 3 days ( sometimes way longer ) in a big cooler before the final butcher/process. Keep it changed... When the water mix runs clear, have no fear... and you will have some really good meat, no matter how old that buck is...
I have used Apple Cider Vinegar to clean old guns!!! lol
I even take a nip for me daily, and add some to critter water...
Acv is wonderful in many ways...
Another vinegar trick: use white/clear vinegar, ammonia and water. I use about equal parts. They make an excellent window cleaner. I buy the off brands and it is very inexpensive. If you have little kids/or want to make sure you think it is a window cleaner, you can add some blue dye. I simply use an empty window cleaner bottle.