After class today, I tried to implement the environment shadow technique that Prof. Bridget showed us, and was fairly successful. To create the environment shadow, I captured a render from a camera that was placed in the same location as the key light. Then, I took that image into Photoshop and painted the shadows in as a black and white map (shadows being white, background being black). I then applied the map as a surface shader projection onto the ball. That render can then be used as a mask for a color correction on the key light layer. My result can be seen below, as well as my environment shadow map and updated nuke tree.
I currently have an animation test rendering on the farm and will post my composite with movement as soon as its ready!