You can use:
- A primer. Since you aren’t a makeup artist, and you might not have a primer already and don’t want to invest in one, E.L.F has one.
- Setting powder (SET. EVERYTHING!!!!!) - I think this would be a good investment product, one you could use on everyone there but also for your own use afterwards. Dermablend has a nice one — they have good, heavy coverage products — and MUFE is always used on me on photoshoots. On the more affordable end, NYX has one as well. Make sure it’s a translucent one though, not everyone has the same skin color and using a colored pressed powder on the wrong skintone would look bad.
- Setting spray. Urban Decay is my preferred, however, MAC Fix+ is popular as well.
However, Graftobian and Ben Nye are brands specifically formulated for theatre & performances and are probably your best bet for stuff like this. If you have a Ricky’s near you you can buy ‘em, or else online. They are really great, pigmented, heavy duty sweatproof brands.