This makeup fx tutorial shows how to create a basic tissue and latex "build-up" wound. These are great for last minute effects and really fun for Halloween. The tutorial shows an arm wound, but the technique can be easily expanded to cover a face or larger area.
Remember to take your time blending edges and creating forms. "Build-up" makeup can often become to large and unrealistic. If built with smaller forms and an eye for realism, one can create a very convincing wound.