Should I use iron remover before or after clay bar?

Use iron remover first. Chemical decontamination can dissolve ferrous particles without rubbing them across the paint, reducing the amount of contamination that must later be removed mechanically. Clay should be reserved for bonded material that remains afterward. This order lowers the risk of fine scratches and often reduces how much claying is needed. Rinse the iron remover off completely and wash or dry the panel before claying, so the clay is not working through chemical residue.