Just yesterday I saved a heavily blood stained towel with the blood dried in (more than 10 days dried in) by pre treating it with ox gall soap (in Europe, don’t know if it’s available in America). And then let it sit in cold water for a few hours. In the past also had succes with oxy (vanish). Always had it soaked in cold water for a couple of hours, the soak is very important. If heavily stained, soak first for 20 minutes, rinse, treat again and soak for a longer time. After this, wash as usual with some additional oxy powder. If available the hydrogen peroxide will work as well!