1. Depending upon desired look, you may need to sand shiplap. (For more rustic look and character, DO NOT sand)
  2. Remove any dust or dirt that may have settled on surface of wood.  Make sure surface is completely dry if you have used a cleaner or any water to clean.
  3. Again, depending up desired look, you may need to fill nail holes with a wood filler (visible nail holes give more character).  Allow filler to dry and then sand until surface is blended well with surrounding wood.
  4. Apply a good quality primer with either a brush, roller or an airless spray gun.
  5. Apply a good quality paint with color of your choice using same manner as primer.  Allow to dry completely.  Repeat as needed, 1 to 2 coats until desired look is achieved.