How do I know when my car actually needs clay barring?

Clay is appropriate when the paint remains rough after a proper wash and chemical decontamination. Most often it is needed before polishing, before applying a coating or sealant, or after exposure to overspray or heavy fallout. If the surface already feels smooth and has no bonded contamination, claying offers little benefit and adds unnecessary abrasion risk. Clay is not automatically needed after an iron remover: if the paint feels smooth once the iron remover has been rinsed off, skip it.