The easiest way for wall bullet holes is to create a textured plain which is transparent except for the bullet hole. When your bullet hits the wall, position the plain at the bullet position and align it with your wall. This way you will get a neat looking bullet hole.
For blood on the wall just do the same, but blood on things that aren't flat is a bit more difficult. To do this you would propbably have to make lots of limbs on your object when you model it, and texture these with your blood texture. In DBPro hide all the blood limbs, and then show them when a bullet hits that limb. A nice effect is to fade the limb in so it looks like the blood is seeping out.
Part of solving the problem is actually noticing that the problem is there in the first place
