Check out this Avengers Hulk my brother made for me. He sculpted the head based on stills from the movie. He attached the head to the body of the 2003 Toy Biz figure from the first Hulk movie and then painted it and dyed the pants. I watched him paint it, and he was concerned with adding the grey hairs that Ruffalo has and the covered-in-dust/dirt- quality the Hulk's skin has in the movie. It took him about a day to paint three of these.
-JT