Using on Masonite wood-grain panel Exterior siding that has many coats, But are all stuck & solid. Looking for most durable SW paint like Sears Ultra.

Thank you for your question. We would recommend to remove any loose or flaking paint prior to using the Weathershield. You should also clean the surface prior to painting to avoid any adhesion issues. Please do a test area first to ensure satisfactory results. Regards, Linda @ Customer Support