My answer might have seemed like a joke, but it's not really.

I used to be a powerlifter and managed a grunt hard core gym. I helped a lot of guys work out.

A powerlifter needs to lift weights, because that's his sport. Tiger Woods did lift weights, but mainly he played a lot of golf and developed the muscles he uses in his sport.

You can work out with weights to build the muscles you use going down hills, but if you want to build the exact muscles you use walking downhill. Nothing is better than working out walking downhill. You need to make it progressive like lifting weights. Start with easy hills. Walk down and back up. Try to do a little more each time. Then move to a steeper hill. Same thing. Down and up. To make the steeper hills progressive. Add a back pack and make it progressively heavier. By hunting season you should be in shape.

If you have access to a leg extension machine. Work out on it 2-3 times a week. It will strengthen your knees.