When repainting your house, here's a way to restore that smooth original finish. After you've removed all loose paint and sealed the surface with a latex primer, use a water-based, exterior grade wood filler to fill in the rough areas that remain. With a four inch tool, spread an even layer of wood filler and smooth it out. When it's dry, lightly sand it, and apply a second coat the same way if necessary. When the surface is perfectly smooth, apply your finish paint.