I bet this will be the easiest thing you've ever done. Dogs love to use their noses. I would even suggest just waiting until your state season starts. Tell all of your friends who hunt during all of the deer seasons to call you every time they kill one in your area. Every chance you get to take your dog to a downed deer, do it and praise him up big time. Just say the same thing to the dog every time and with great excitement, like "sniff 'em." Even if you know right where the deer is, bring the dog to the site and encourage him more than you ever have when he starts to smell the blood. Even if the deer went straight down, take the dog to the downed deer, say "sniff 'em" or whatever phrase you like, and let him wonder about until his attention goes to the downed deer. Don't show it to him or point it out to him, but let him acknowlege the dead deer. Act like you don't know it's there, and when he acknowleges it and goes to it, praise him up like he found something you were missing. Do this as many times as you possibly can, and the dog will start realizing when he smells blood that its game time. Just make it a game.