Use clay bar or synthetic clay towel to remove (microscopic) high points of left over minerals then follow up with water spot remover (mild acidic cleaner) to remove (microscopic) low points. My preferred water spot remover is Optimum MDR as it is a gel like substance that better adheres to paint for longer dwell time. Many other brands have spray on water spot removers that could work as well. If mild cleaner does not completely remove, consider going to pro detailer to use diluted wheel acid cleaner (much stronger acid).