The bottom one is easier to get a good finish on because it's entirely aluminum, but the top pieces both have a rubber gasket integrated into their finish that seals up against the glass. Regardless I sanded all of mine down and painted them with DupliColor Trim Paint over 15 years ago, and they still look great.
In my case I didn't sand off the rubber gasket part off of the top pieces - just the top surface that had been peeling/corroding, if that makes sense.