Try the site below. I never had one trained by anyone. a few mock blood trails or even drag around a boned out leg from a deee and let them find a prize like that bone at the end of the trail has worked on a few dogs for me. JCB uses some bloody meat in a sock to make the trail.
http://www.texasbloodtrackers.comI did similar to this. I started when my pup was very young made trails out of her food, a piece every few inches then further, then would go for longer bits with only dragging a piece of food. When she got that down I saved some blood from a deer and cut a piece of hide and used that. She successfully found 2 hogs that I couldn't and a deer that I just let her loose on instead of tracking it myself. Last weekend we tried trailing a hog that was wounded, she was continually on the blood before we would find it, but never found the hog, it was a lower leg hit, don't think it died. The more you use them for it the easier and better they will be.