As I've been learning more about what ZBrush can do, I decided to experiment going between Cinema 4D and zbrush to clean up the James model. He had a lot of issues in his mesh, especially with his face, which didn't come out very well when I built it from scratch. The image below is after plugging some holes, removing a bunch of skewed polygons, some remeshing, and some fine tuning. His face looks a lot cleaner, though it's not done yet, but I think it's a vast improvement from where it came from. 
I will probably end up importing the entire model into ZBrush to clean up the jacket, hair, and anything else that I had not build myself, and paint him in there as well, to hopefully give him a more natural look. Time will well, as I also quest to learn another program this month - Maya.