The idea of this instructable is to explain the basics of how simple fake wounds are made. In the picture of the end result, the makeup and general colored area is focused in one spot, which makes it look a bit more fake than wanted.
This problem can be fixed in two ways:
One, create a more logical design for a cut. In this instructable the leg seems to look like it was scratched by a ferocious, infected, three-clawed beaver; smeared with mud from a lake, (which would actually make sense if there was a beaver around); and cleaned around every area except for the cut itself. Unless that's what you're aiming for, try to think of what actually gave you the injury before you make the design.
Two, adding more paint or makeup around the area makes the cut, bullet hole, or burn look dirtier. Even if your doing a small, simple cut, you have to keep in mind what the surrounding skin would look like if the cut was real. A deep cut on a finger might flood blood to one area while the rest of the finger turns pale. You don't want to be left with a single area untouched while the rest of your body is clean.
-Black, red, and brown acrylic paint. (For dirt and infection, it's nice to have a mixture of green and yellow on hand)
-A bottle of fake blood. (Found at nearly any costume shop, though it is a simple process to make your own)
-Scar wax (You an find this at practically every costume shop, too)
-Flour (For an alternative to texturing with an easily available material)
-A large needle
-Newspaper (Unless you enjoy mopping fake blood off the floor)