Dry the redwood railing completely before you start the painting. You should never paint redwood when it is wet, because the wood absorbs moisture readily and wet painting could damage it.
Decide whether you want to paint or stain the redwood railing. Redwood takes stain quite well, and that stain helps to bring out the natural grain of the wood. There is no need to paint redwood for protection, but you can paint it for appearance if you wish.
Apply a primer coat to the redwood railing. Follow the recommendations on the package when applying the primer. Allow the primer to dry completely before applying the paint.
Use a wide paint brush to apply the stain to the redwood railing. Brush in the direction of the wood grain for best results, and use a brush with natural bristles. Wipe away any excess stain, then allow the remaining stain to dry completely before applying another coat.
Brush the paint on to the redwood railing with a wide natural bristle paint brush if you prefer a painted look to a stain. Brush in the direction of the wood grain for best results.