These discussions about aesthetics and "curb appeal" always make me wonder about people's priorities.
A pretty engine does not make it reliable. The factory castings normally clean up well with soap and water without any other help. All media blasting does is create pours for the aluminum to trap water, then it turns into a dusty white powder coating on the surfaces.
Painting is not suggested, especially the colling fins because that acts as a heat barrier insulation and will retain a lot of heat, that defeats the purpose of air cooling the engine. The majority of the cooling fins are covered on purpose with air deflector tins so the engine flywheel fan can route forced air across the cooling fins.
Most factory-built engines do not have any paint applied until all covers are in place and the engine is ready to be installed on the machine. Some engines have no paint except for the main crankcase and that is it.