Summarize the following:
Liquid latex is good for achieving a generally deathly look, as well as building up wounds or other facial deformities.  You should be able to find it at seasonal Halloween supply stores, or at beauty supply chains. Choose a color that looks appropriately pale and decaying. By selectively ripping parts of the liquid latex, you can put wide gashes or small lacerations into your new skin.  Use scissors.  You should carefully snip the latex until you create the wound you want.  Be careful not to nick your skin! Use a toothpick.  Simply stick it into the liquid latex and drag it through for a gaping wound.

Summary:
Purchase liquid latex. Put wounds or scabs into latex.