I printed out a picture of the punisher skull I found online. I then put a piece of wax paper over the picture. I traced the image using a pen/pencil onto the wax paper. Then I flipped over the wax paper and put 3 pieces of wide blue masking tape over the traced outline making sure that each piece of tape overlaps the next. Flip over wax paper again and use an exacto knife and cut the trace line you drew. Then you peel off the wax paper and the masking tape acts like a sticker. The ammo can was originally the green color of the skull so I just put my "sticker" on the can before I started to spray my first coat of tan paint.
Thanks, I just finished up painting my first rifle stock, barrel and scope like this. Having something to practice on first takes all of the anxiety out of actually doing it on a rifle.