Don't get lazy

Thought I was doing the clever thing by squirting Mav regularly to rinse off any salt as we live about 600m over hill from beach and regularly drive along coast road. I've been lazy by not chamoisying ( is that right? ) down afterwards and now have very reluctant watermarks on glass except where wipers sweep windscreen. Have tried jiff which helped but need advice about next step. One thing I remember a neighbour using years ago was bon ami and thinners but haven't tried this yet.
Hope someone can assist, thanks DRC.