what you have there looks alot like a bite or gravel rash from a road accident or possibly that flesh eating desease.
done some of this in my mispent youth mostly with skin putty and nails with bload, some latex, best way to get a groove is to use a matchstick cut to size and covered in vasalene or better ky.
isn't our tom the undisputed expert in this field, something about a death mask for one of derrens episodes.
