It really is up to you in the end and how you feel about keeping the guitar 100% original.
I have refinished several
neck plates and I tend to lean towards Krylon High Gloss Black. First make sure it is completely clean (duh). Anyway hit it with 600-800 grit lightly just to fog the surface, don't worry the paint will fill the very light scratch marks. Remember as always two to three light coats will turn out way better than one thick coat.
When you do paint it I recommend doing it on a piece of cardboard and laying it outside in the sun for an hour or two. Sure it heats up but the sun tends to bake the paint on better than just an air dry. The biggest thing you need to think about here is that your going to find it impossible to create a cosmo black finish if thats what your looking to get, give up before you start.