Step 1: Grow a beard
Step 2: Painting the jacket
For the front design I borrowed most heavily from the first movie, with this page as my main template. Starting with the second movie Wolverine loses the spiky design (which was a nod to his original comics costume) and gets a big X on his chest that I don't like as much. The more angular design on the arms I stole more from the third movie. All three movies have a really dorky back design, so I just made up my own for that. Don't forget the little "x"s on the collar and the bigger one in back.
For the belt buckle I just used a button maker and yellow and black construction paper, and attached it to the belt that came with the jacket using a strong rare-earth magnet. The color was a little cheesy looking in good light, but it worked fine in the dark.