He will clean the blood off if he has soil to bathe in. Chickens use the little nodule (greaser) next to their tail on their back to acquire oil to shine their feathers. It is the chickens instinct to preen with this oil. Chickens bathe or "Dust" in soil (clean soil) to bathe. Humans use water to bathe. You can make a "dusting box" and put it in their coops if they are penned. If they are outside they will use the soil they find to bathe in. Washing a chicken in water removes the protective oils they have put in their feathers. It is not natural for a chicken to bathe in water.
My roo got quite a bit of black on his comb but it looks like it is healing already. But he has a nasty patch on one of his wattles that I am worried about. It is black and hard, but it seems to be sort of flaking off on its own. The skin under it looks pale instead of red.
But, overall he seems in perfect health and the area is no longer swollen. He let me massage in some vaseline with no objections...... What else should I be looking for?? We're in for another cold snap soon!