1. cut/apply checkerboard stencil
2. light uniform coat of lighter colored paint
3. north to south dry brush with a course brush to add fiber effect
4. tint top and bottom edges of each square
5. let dry/remove stencil/apply inverse stencil
6. repeat steps but brush east to west and tint E/W edges.
that'd be how i'd do it if i had any clue how to run an airbrush.