Pry loose the planks surrounding the barn with your crowbar, taking care to keep the boards as intact as possible. It will be difficult to reuse the wood if it comes off splintered and damaged.
Examine the removed boards for any lingering nails or screws. Use your hammer or crowbar to pry them loose in order to make the boards as clean as possible.
Brush the boards clean of dust and cobwebs with your brush. You can also use this opportunity to give each board a closer look, keeping an eye out for any rotting or damaged pieces that need to be thrown out.
Clean the boards with the pressure washer. This will help restore some of the original quality of the boards, and reduce the impact of years spent in harsh weather.
Set the boards aside to dry. Let them sit for several days to ensure that they are completely dry before finishing them.
Apply several coats of your preferred varnish to the boards as a final finishing touch. Once that is dried, the boards should be ready to be put to use in a new home.