Protect any plants in the area you intend to clean by covering them with a tarp or plastic sheeting.
Make sure the gun of your pressure washer handle is in the "Off" position. Choose a 25 or 40-degree angle spray nozzle for your pressure washer and connect it to the nozzle tip. Check the oil and gasoline in the pressure washer to make sure they are at the proper levels.
Connect your garden hose securely to the pressure washer and review for leaks. Prepare the detergent solution as stated on the container's label. Immerse the detergent strainer into the detergent solution.
Turn the trigger gun to the "On" position. Squeeze the trigger several times until water begins to flow. Spray the entire stucco wall with the pressure washer, starting from the bottom and working your way to the top to avoid streaking.
Set the trigger gun of your pressure washer handle back to the "Off" position. Secure the detergent spray nozzle onto the end of the gun's wand.
Unlock the trigger and spray toward the ground. Begin spraying the stucco when the detergent begins to flow. Spray from the bottom of the wall to the top.
Turn the gun back to the "Off" position and disconnect the detergent nozzle. Turn the gun back on and rinse the detergent from the wall, working from the bottom to the top.