Hi. About the only thing different for this is that you do not want to paint until the surface chemicals have been washed off. These can cause adhesion problems. When you have completed the railing, let it "weather" for a month or two, depending on the amount of rain you get. The more rain, the better. Then pick a day when the wood has had a chance to surface dry for a week or so with no rain. Prime, paint and enjoy. By the way, wood expands and contracts with changes in moisture. Be sure that your design allow for you to tighten lag bolts or similar when it has shrunk.