1.Be sure that all cracks and openings in the siding are sealed with a quality acrylic or siliconized acrylic caulk
2.Treat any mildew that is present with a solution of one part bleach to three parts water.
3.Remove dirt and dust from the entire exterior by power-washing with plain water, or cleaning with a detergent solution and rinsing thoroughly.
4.If any old paint remains that is flaking or showing other signs of poor adhesion, remove it by careful wire-brushing, working in the direction of the simulated wood-grain if there is any.
5.To help your paint adhere to the fiber cement siding and to get the most uniform-looking finish on your paint job, the best practice is to apply one coat of a quality exterior latex stain-blocking or masonry primer to all of the siding.
6.Complete the paint job by applying a top quality 100% acrylic latex paint that is recommended for use on masonry surfaces. You can extend the life of the paint job by applying two coats of paint.