Try this. Do a thorough cleaning with Dawn dish soap, rinse with a damp cloth, and dry. Then use M-Ron Glass Wax. It's a thick liquid that dries to a powder. Once dry, buff off with a microfiber towel. The powder can come off like dust so cover the dash with a large towel. The waxy coat resists dust, dirt, and it makes it easier to remove the oily residue with normal cleaning. It costs about 20 for a 12 oz bottle (on AMZ or eBay).