I’ve been polishing my windshields for years with Bon Ami 1886 Formula powder. Keeps the windshield smooth and free of contaminates that can cause chatter. The stuff is even referred to specifically in a factory BMW service bulletin about chattering wipers.
The 1886 Formula is hard to find, but I get it at little independent hardware stores locally.
I usually wipe down with a tar and adhesive remover first.