carry a roll of orange surveyors tape with you, as you blood trail the animal tie a strip every so often about head high say every 20 or so yards, that way if you lose the blood trail stop and look back for the markers they will tell you basically which way the animal is traveling, at that time I begin a back and forth search, think like a half circle only seperate the back and forth search about 10 yards apart as you move foward enlarging the arc as you move foward. some where in there you should find blood and begin the marking again, you want to go slow and be as quiet as you can, and watch ahead of your search, THE MOST IMPORTANT THING I THINK IS WATCHING WHICH WAY THE ANIMAL GOES AFTER THE SHOT, THEN GIVE IT SAY 1/2 HOUR BEFORE THE SEARCHING. And check everything a wounded animal can and will hide where you think there is not enough cover to hide a mouse. This process has worked for me for years when trailing a shot animal.
I use toilet paper to hang on a limb above the blood
When I lose the blood I walk back to the last several pieces of paper and get a line of sight to give me a true direction of the animals trail
If I lose it from there I start making half circles arcing back and forth until I find the blood again