There are many choices on the paint and how you paint the wood. No matter what you choose to use I would try to do three things to assure a long lasting finish that will hold up for years, especially in the sun. I would try to use a marine grade of paint and if I couldn't, I would use a marine Spar-Varnish as a final coat to keep the sun ultra-violet rays out and whatever water got on the finish from runing it. Even more important, I would paint ALL sides of the lumber, the top, the bottom, the side edges and the end edges. In other words, seal the wood from all possible mositure. It works and you will enjoy the look of the finish for a long time if you follow these ideas. Most likely, because of the number of coats of material you will have to apply to the lumber to achieve the goals I have listed, the finish may come up on the glossy side, but I would not let that stop me.
