I've been training bird dogs retrievers ect since the early 70s
Heres my short simple way to do it...
Basically when you gut or hang a deer try to recover blood from it and freeze it, if you have some buddies that will help get them to recover as much blood as possible everytime you or they kill a deer.
Now freeze it, film canisters or small tupperware type containers work well.
Next the training,
Put a harness on the dog this will teach the dog to associate the harness with the tracking job at hand. Use this harness for tracking and nothing else.
Now the rest is simple take the frozen containers of blood and mix them with a gallon of well water ( dont use chlorinated water) then lay a trail with a gallon milk jug with holes punched in it so the water/blood mixture drips steadily on the trail. one film canister or small cantainer of this size per gallon will work well. wear rubber boots to conceal your scent you want the dog to track the deer blood not you.
First trails should be straight and maybe 25 feet get the dog to track them, and have a reward on the end, hot dogs or any dog treat the dog likes will work. do this once each day for a few days so the dog learns that there is something real good for him at the end of the short track.
Next gradually make them a little harder first longer in a straight line the start to make right angle turns so the dog learns to backtrack and pick the trail back up.
Dogs pick this up real quick, little dogs like dachounds and small mutts work well because they are close to the ground and naturally ground trail, but labs and shorthairs learn it quick also. The nice thing about little dogs is they wont jerk your arm out of the socket trailing, a big dog in a harness can pull like you cannot believe.
DO NOT DRAG A DEER HIDE!!
The reason you are going to the trouble of collecting the blood is to teach the dog to track blood trails not deer, anywhere you kill a deer there will be lots more of them, you want the dog to track blood trails only.
When you actaully do this in the field wear orange and have some assistants that hang back if possible wearing orange also. have one of them bring a 22 pistol if legal, in case you need to dispatch one( check regs).
You can place deer road kills at the end of trails when you get to the advanced part of the training, then really praise the dog when he finds it and give him his treat.
thats about it.
Key points
1)no deer hide drags, just blood
2)dog always on lead while wearing tracking harness , otherwise the dog will leave you behind and is in danger of being shot during gun season, never use this harness for anything else but tracking.
3) you take the few weeks it takes to train this and you will never lose another deer
4) let other deer hunters in your area know you can do this to give the dog ample practice each season
5) love your dog