I've read that some people just spray the black near their armor and let the wind carry it over to land there.
I used to paint a lot of gaming miniatures back in the day and I would dip a toothbrush (hard bristle) in a blood color and run the tip of my thumb through the bristles to make the bristles fling the paint in a spatter.
Instant blood spatter!!
This should work the same with the black mist on the armor as long as I use very little paint so that it gets more of a misted effect, don't you think?
If anyone wants to chime in on the misting methods I would be glad to hear them. I want to try out several methods before commiting to something. Thanks!!!