Obviously, exterior plantation shutters require a bit of a different tactic since they are harder to reach, but all-in-all, they should still be fairly easy to clean.
First, start by pressure washing or using a hose to get all the loose dirt and material off of the shutter. If you have a powerful pressure washer your job will likely be easier since it will be able to remove most of the dirt on its own.
Second, safely set up a ladder to access the shutters and set yourself up with a brush or cloth and a bucket full of your chosen cleaning material. Dish soap and water will likely work well for most cleaning, but some bleach could help remove stubborn mold or other marks. If you’re using any cleaning materials harsher than soap and water you may want to test scrubbing in an easily hidden area first to make sure you won’t discolor the shutter.
Third, use a dry item like a brush or cloth first to remove any dirt particles that were loosened by the water and then follow up with a wet cleaning material to remove stains and marks. Be sure to rinse off the area well before going on to using a different cleaning material.
Finally, make sure you hang your shutters for a day or two before replacing them to make sure they are completely dry and any water stains have dissipated.
Simply scrub the shutter clean using the brush or cloth, making sure to stay safe if you’re on a ladder. Once you’re done, continue hosing off all the shutters to remove any remaining soap.