For my Dead Dale zombie outfit I used a mixture of watered down red and black acrylic paint (depending on how "fresh" you want the blood to look you would use more or less black). It splattered nicely and stays on the fabric once it's dried. Then on top of parts of the wounded area I added some more homemade blood (corn syrup, chocolate syrup, water, flour, and lots of red food dye) that has a shinier look but does wash out.
Here's us as a Little Zombie Girl and Dead Dale from AMC's "The Walking Dead"
http://www.cosplay.com/photo/3212895/
Hope that's what you're looking for!