Excellent article indeed! Having tracked the blood trails of a few deer, elk & one memorable bear, I would only add that I have found it helpful to have some surveyors tape or similar to mark the blood trail as you follow it.
Mark it every 10 to 20 feet or if following a faint trail, every time the trail thins out. In this way, you can turn round & easily see the general direction the animal has taken to that point & you may get a better idea of where it's heading.
It also makes it real easy to come back to the last place you had sign when casting around looking for more blood or hair on a faint trail.
Like the idea of the GPS as well.