We're doing this trip at the moment, in a C182; and covering both West and East sides. Happy to answer any questions. I'd advise going to the smallest airports you can, they are much cheaper and easier to negotiate. Accra, which someone mentioned, was one of the biggest hassles, and the most expensive stops, so far. Bobo Dioulasso in Burkina Faso, or maybe Cotonou in Benin, have both been much better.
Website with trip info at
katamarino.co.uk - Adventure Flying Resources