Painting a MH is easier than painting most cars and certainly easier than painting an airplane. You are dealing with large flat surfaces rather than a bunch of curves, hood, trunk, roof, etc.
At the factory there will be several painters on a coach to keep the paint flowing and the surfaces wet. When painting something that big, you need to break it into sections that you can handle by yourself. With most coaches, there are seams, or other breaks, that will allow you to mask off one area at a time for you to paint. It is not that difficult as long as you do not try to tackle more than what you can handle alone. A moveable scaffold helps to give you access to the upper sides. As far as vehicle painting goes, MH's are easier than a lot of other vehicles. One other thing to consider is that when you break the coach into sections, it allows you to buy paint as you need it and not "guess" at how much total paint you will need.
Be sure to closely monitor the temperature and humidity and mix your paint accordingly.