A few tricks I learned today on getting out fake blood stains from your zombie's clothes..........

If the stains are still wet, keep them wet.

Then you can put baking soda and vinegar in a bowl and soak the zombified clothing.  Let it soak for at least 30 mins.

Hydrogen peroxide is also a good choice.  Just blot the stain with a white paper towel.  This works better for white or lighter clothing since it acts like a bleaching agent.

Hairspray:  Not natural but works pretty well.  Spray hairspray on the stain, let sit a few mins, and wipe away the stain with a damp cloth.

Lemon:  Cut a lemon in half, rub the stain, and then pour salt on it.  Let this sit for about 10 mins. Lemons are a natural bleaching agent so be careful with colored clothing.

That is it.
Zombie on.