Here's the complete set. I've done a lot of work on the Rau, less on the Kakama, and just enough to see the base color on the Akaku. I'm thinking of picking up a set of dental scrapers from Walgreens or somewhere to get the nooks and crannies; the Rau is nice and clean now but there's still a lot of stuff that needs cleaning out.
Closeup on the more special masks; I might try repainting the Kakama with black edges if the dental scrapers don't work, just to hide the patches of gold.
And here's the other three, turned to show base color. Honestly not worth saving; I've already got plenty of the default colors, and a bunch of artistic sisters who'd love to try some mask modding (and they're not nearly as amateur, to boot).
I really can't tell what the paint is, but the silver on the Akaku is more resistant to rubbing alcohol and it's bothering me a bunch.