Step 1: I added liquid latex and cotton to the parts of my hand which I knee was going to be exposed, this helps mimic the ligaments inside the hand. I also made the bones with liquid latx and cotton and molded until I was pleased with the shape.
Step 2: I went around the entire edges with scar wax, bleeding one side into my skin and lifting the other side up, this will mimic your skin folding with the tear has happened. I then went to add cuts into the wax to tapper off the cut.
Step 3: I then went on to add colour when I was completely satisfied with the mold. Used a red water paint for the entire base, and added black to make some parts of the rip appear deeper, if parts were too dark I'd add water and blend it out. I also added a bruising texture to the wax for a better effect.
Step 4: finally I added a drippy blood to the wound and made it more grose by adding scab blood, but not to much.