For detergent-based blood (good idea, generally, for cleaning costumes) MAKE SURE that your actors don't have allergies. If possible, if they don't have allergies, still start with hypo-allergenic detergent. I love the blue-detergent idea, though, wish I'd tried that before!
For two show days; there's no way around it if you're using liquid blood, you need duplicate costumes. Bring this up right now with your production team, because if they haven't been planning for it, this could be difficult to fix now.
You could also think about using non-liquid coloring on the clothing; the clothing piece is always "bloody" but just covered. Say the character who's shot/stabbed/bitten wears a coat when stabbed; then removes the coat to get to the wound, and oh look! there's blood everywhere.
just some ideas...