There's nothing you can personally do to improve the looks. Anything you do will make it look worse. Cold Aluminum Blacking won't take unless the wear is actually through the frames anodizing. The black is only color added, not the anodizing itself. Anodizing is pretty hard and holster wear alone won't usually wear through it. In order to have something you'll be happy with you'll have to have it done professionally. You can have the anodizing on the frame redone, or have it refinished with one of the spray on finishes: Duracoat, Cerakote, etc. If you don't want to go to that expense, it's really best to just leave it alone.