Two questions first. Do you have good experience painting cars and how professional of a job are you looking for? Painting a M/H is no different, just bigger. I certainlly would not reccomend learning to paint on your coach. This will be a very expensive endevor and could be a disaster if you don't have the necessary skills.
If you decide to proceed, I would strongly suggest using a two step paint, base coat then clear coat. Depending upon the size of your m/h, the materials alone will be in the thousands $$$.
I personally have painted many cars including some show winners but decided against painting my coach. I had it painted in Red Bay, AL at Custom Paint and the bill was %6,000(36' Allergo Bus). Bob