To answer seriously, try this:
Get your undercoat in order first. Then prep it for the splatter coat: light sanding probably.
Now you want your (presumably) bright red paint (probably a lacquer), and a no. 12 paintbrush, and a stick of scrap lumber.
Load your brush, and position your stick perpendicular to the orientation of how you want the blood splatters to drip. Whack your loaded brush against the stick, and let the splatters fly.
Repeat as desired.
EDIT: Practice on scrap first! And also, probably you should think about how to orient the body so you get things to drip right - gravity can be your friend or your enemy.
Have fun.
Bagman