I had a Jagdterrier I was training to blood track. He loved it as much as he liked flushing birds. I think upland hunting makes a dog understand what is at the end of a blood trail. I used a different training method than is usually discussed. Instead of what one finds in "Tracking Dogs For Trailing Wounded Deer" by John Jeanneney. I make it an extension of FF. This gives me a good handle on the dog. The dog realizes he has to perform for me, first, and then himself, insead of doing it for himself and then me. This might be subtle but it makes a difference in my opinion.
The first blood tracking I did 30 years ago was illeagal but the DNR didn't mind. We would grab my old lab bitch and put her on the blood trail and I don't remember losing one. I didn't always ask the local DNR agent but he was a good guy and didn't want to see anyone lose a deer. My lab loved to track crippled birds. She didn't cast the line and try to guess where the bird was going like a lot of labs one sees nowadays. She followed the line. If the bird or deer turned she did. When she picked her head up you knew she was going to find it.
I live in the UP of Mi now. I am under the same contrainst as the gentleman from Wi. The dog must be leashed, dispatched with a knife. I put the knife on a 3 foot pole (read spear). I don't know if this is legal but it is effective.
Dr Fatguy