I will defer to Harmonyards, he has a lot more experience with paint than I do but he points out the issue is the silver paint. Silver or any metallic paint is almost impossible to match. I have had some luck with Testors ELO and also Klean Strip Prep All on lettering but have not tried it on Silver. If you try any chemical, try it on an inconspicuous location for a few minutes to see if it attacks the silver. I usually use a wet Q Tip to rub the area.
Pete