PVA is water soluble, so it won\'t damage any tools you use - especially if you use a brush to add the red (Be sure to mix it thoroughly, as if you\'re using white PVA the blood might end up slightly pink!)
You also don\'t need to worry about PVA being brittle, as when it dries it becomes rubbery, and will not be damaged by knocking.
However, due to it\'s limited strength, it may \"rip off\" of the surface if it is pulled.