KBS Coatings has a direct to metal clear which I used on my polished aluminum gas tank but it has a gloss finish. If you spray it on from a distance, it might kill some of the gloss


'66 C60 body, '97 C6500 chassis, '07 LBZ Duramax with Allison 1000
https://photos.app.goo.gl/cxwv1C6Ay2oxYH7u7