I've seen all kinds of remedies but this one really works............I have 2 of these units and after a 20 hour butt cook, I can have the inside of the window completely clean in 10 minutes. Simply go to Dollar Store and buy a $0.99 bottle of "Awesome". Get some paper towels and spray side to side starting from the top. You will immediately see the grease running. Keep spraying, working from top to bottom and wiping with paper towels. This method really works!