Yes, you can, though it can take more time and require more elbow grease to accomplish. There’s always the good old pole brush or hand brush that you can use, but this can be tiring, potentially backbreaking and tedious work if you have large walls. Handheld brushes are always an option, but if you don’t have a pressure washer, it’s more convenient to find a company that leases them out. Better yet, you may hire a wall cleaning expert on Airtasker.