A clay bar can remove some overspray, for example acidic chemicals like tree sap, but for contaminants that are more stubborn such as oil based paints, cement, polymers and so on, it will not do that much. In fact, the clay bar would be more of a step to follow through once the contamination overspray has been removed. Although a clay bar will not remove your clear coat, it can cause micro-marring if used too aggressively, this is where a machine polish comes in handy to rectify and correct these minor blemishes. The effectiveness of a clay bar heavily depends on the severity of the overspray and chemical being used.
