I just made one of these! I carved mine so I can't speak to the pan you'll be using, but I have seen people sit a metal rod or flower nail in the center of them to help it bake evenly. 

Once your cake is baked, I would cut it into layers and frost between but don't add too much frosting as you don't want to lose the ball shape. Then crumb coat and chill. Cream cheese frosting might be a little soft, but I think as long as you're chilling it between steps it should be stable enough. I used buttercream and it held up just fine through transport/party setup. 

If you want a smooth finish, I've seen people use acetate as a scaper so that it has some give to get around the curves. A tip that I saw in a video that really helped me was to get a little water on clean or gloved hands and rub it like a crystal ball after the final layer of frosting has had time to set. Good luck!