Fix the Lens Body scratches?

I have a number of vintage Pentax prime lenses from 28mm f2.8 to 500mm f4.5 (circa 1955). Is there an acceptable method to fix/recoat/cover nicks and scratches on the exterior surfaces of the lens body?

Permanent magic marker ? (would rub off)

Spot Cold bluing ??? (ref: Birchwood Casey Aluminum Black)

Spot anodization ???

Spot painting ??? (ref: Birchwood Casey Super Flat Black )

Something else ???