The S in my side marker on both sides is faded or peeling. I'm not 100% sure if it's paint or a sticker.

Regardless, are there any proven methods to get that red S looking sharp again?

Otherwise, I'll just brush paint some red in there, but I thought I'd ask first...

 

Yeah - I used Testors metallic red model paint. I purchased it at a local RC hobby shop in a 1oz bottle. Sorry, I don't recall the specific paint code or #. I applied it with a pinstripe brush and clear coated with nail polish clear.
The reason I used a metallic paint - If you look closely at the "S" on the rear hatch; it has a little metallic flake to it.
You can also go with a red fingernail polish; conveniently found at some grocery stores or Walmart.

 

picking at it a little bit, it seems like that red is originally a sticker. i may peel off as much as i can before painting.

i was thinking fingernail polish at first, but i like the idea of the testors paint. heck, i may have some red laying around that i could use if the paint is still good...

 

I applied it with a pinstripe brush and clear coated with nail polish clear.
The reason I used a metallic paint - If you look closely at the "S" on the rear hatch; it has a little metallic flake to it.