Krylon.
Prep is going to determine how well it sticks. If I'm painting it I plan on never trying to "restore" it. So, light scuff with 100-120 grit. Xylene or acetone wipe to clean with lint free cloth. After it's dry, another cleaning to make sure it's fully degreased.
Then I make puddles on a sheet of cardboard and sponge it on. My kids enjoy this, dedicate a sponge to each color and just keep layering whatever they think looks good.
After 24 hours I do another wipe with xylene, and paint it with satin clear. 2-3 coats until it looks nice and wet.
After a week or so when it's fully cured out I buff the whole thing with some fine steel wool. It really cuts the shine without digging in and sanding the clear off.
I'm sure there's some science behind it, but I've never found any colors very durable and the matte "camo" colors even less so. The clear is actually surprisingly tough, and I haven't had any noticeable amount of wear after 5+ years on some of them.