On the big barns they use to 2 full sheets( 1 sheet of plywood is 4x8') Because I only have mine on a smaller barn, I cut the plywood into 2 4 foot squares. First I sand down the board and paint on 2 coats of outdoor white paint. Then draw on ur design with pencil. I do check to sqaure up my board first. U can use any outdoor or craft paint. Use the blue esay release tape to mark ur sqares so u have sharp lines. When each section is dry u move ur fresh tape around to make the different blocks. I paint several coats of paint on each block for a truer color. When u r done with your quilt block either spay or paint on a silcone weatherproofing. I usually paint all the same color at once then move on to a different color. I have put designs in the blocks, trying to make calicos, dots etc but really does not show up from far away. I have a freiend who lives in the city, she has 1 on her garden shed. People are always stopping by to tell her much they enjoy her quilt or enquiring on how to make one. I have my block setting on a piece of white angle iron in the peak area of my shed. Then to change it all DH has to do is go up on the ladder and take out a couple of screws.