You will have to repaint it all if you are going to paint them or touch them up. Thin your paint and it will lay down and level better. Polish the bright work before painting...you will affect the paint finish if you try to do it afterwards. I have seen guys carefully sand with 8000 grit some brightwork to give it a uniform finish, but like I said, it is plated so you really really have to be careful because it is plated. Don't recommend you sand it, use polishing compound and buff wheel and see if green or blue will bring up the luster you want. Then wipe it down with a good thinner a couple times to strip any wax residue from buffing before you repaint.
If green or blue won't bring a luster drop back to white and then go to green or blue compounds.
Repaintsupply.com carries SprayMax 2K in a urethane gloss clear that is excellent for paintwork and it is fuel proof. It is a 2part activated isocyanate type urethane and requires it to be used withing 36 hours at most from when activated and it requires proper protective mask and skin protection. The paint has lethal chemicals and can/ will kill you if you don't take precautions.
But it is great stuff if not a little spendy at 18-19 a spray can last time I priced it a few years ago. It has limited shelf life unactivated and an expiration date on the can for use by...