Did some test with a quat chemical, a month ago I sprayed various parts of my house & garden with some quat based cleaner, I knew they worked slow and this was putting me off using them but the results I have seen on my test sample make me think I could do the work then offer to invoice the customer a month later when they see a result.
Here are the photos the bay window was equal all around and I treated one side. The gate I treated the left top side, the shed I treated the front ( which is in the sunshine so looks brighter)
