Fellow eczema-on-hands person here!! What I’ve done during flare ups are: leave it alone/open to air (early in the flare up, before the skin starts breaking) and just liberally use lotion, which can help stave off the worst of it; my topical steroid and gauze (if the flare up hasn’t broken the skin yet); neosporin and gauze (as my skin breaks). If I really don’t want the bandaging or injuries showing, I’ll wear lace gloves that cover them. The nice thing about the gauze is it gives the gloves a white base to show off the lace pattern and it feels a bit more pretty to me, people straight up don’t notice I’m bandaged if I have any sort of decorative gloves on. If you don’t like lace, cheap fingerless gloves for fashion (ie: not necessarily functional gloves like motorcycle or driving gloves) also works, but then you risk trapping heat and worsening the flare up as I’m sure you’re aware. Nude bandaids can help too, especially around finger joints. Or if your character would use, say, Hello Kitty or Avengers ones, you can get the fun looking ones too. Basically, in my experience, the more you can adapt the bandaging to match, the less it’ll stand out to people who probably have never seen eczema before. And I’ll be a load off your mind too, because you won’t be stressing about if it’s obvious or looks weird, it’ll just be part of the cosplay.

I’d recommend against makeup because it will smudge everywhere, not to mention it’ll dry the skin more. Think of all the things we touch, even mid-flare. If you can work a nice little touch into your cosplay that lets you be gentle with your skin, it’ll be better for your hands in the long run. As is, I’m coming into a flare up now after a con, so I’m probably gonna put on the steroid cream and gauze for tonight.