Hi, gave a spare rail that was cheaply coated (slightly rough) as a test piece to an artist in the family. She kindly drew a proof of concept in pencil, however I would not know how to protect this while installed or whatever the best medium would be for the final piece on my RIF - paint, watercolour ground, pencil. From some brief research clear matte Duracoat, Alumahyde and cerakote were mentioned, though apart from a Jeweller suggesting to heat the metal then apply wax pencils in layers there seems to be no information on protecting artwork on metal. She already has further ideas but not being a professional applicator some advice would be appreciated before I appropriate more expensive parts; advice on sealants for nylon and plastic as well as how to prepare the relevant surfaces would also be helpful. Thanks in advance.