You need to distinguish between a 'polish' and a 'wax'. A polish basically cuts surface discoloration from the paint leaving it looking shiny. A wax sits on top of the paint, but to look good usually requires the paint to be 'surface cleaned' first. I have graduated from polish to waxes such as Autoglym high-def wax and find it more effective than new car paint treatments. But it's about £40 a pot.