use a claybar, meguires do them ,about £20 from halfrauds or check ebay should get them cheaper on there ,hard work but the amount of crap it gets out of the paint is amazing , ive always used meguires 3 stage polish and thought my car was clean , claybarred it friday and omg .amazed by the finish ,finished it of with meg colour restore 2nd stage of 3 stage polish and then did the 3rd stage to finish it of , glass like finish and a shine like a new motor , worth doing