I have been on alot of bloodtrails with friends, family, and by myself. I only look for blood, mark it with toilet paper, until I find the deer. I have a knack for finding blood and downed game, so everyone seems to call me ( I actually get a kick out of blood trailing deer). When the blood trail stops I go pick up two of my deer dogs and they usually find them quickly- but I save the dogs for very last because I like to blood trail.
A good deer dog/ blood tracking dog is very reliable and easily the best way to find a deer. No human blood tracker can ever compare to a experienced nose of a dog....