An even easier way to clean the casette is to remove it and immerse directly in solvent. Its wasy to remove, all you need is a chain whip and wrench. Once you know how to do it you can also swap casettes to your hearts content! FYI, I do use the park tools chain cleaner, it works great. Also, remember, you don't need to get it perfectly shiny clean, the goal is to remove grit and dirty oil, since all you are going to do is lubricate it again anyway.