Hard to saw without seeing the actual footage.
However, as far as facial sweat, I’d say use Mocha to track masks around the facial features, to isolate the sweaty skin.
Then reduce any specularity — any shinyness — One way would be to “clamp” the highlights using Levels and “clip to output white” ON, and set the output at the brightest skin tone, but darker than the specular, glistening sweat.
Adjust the gamma to get the skin tone right while clipping off all the specularity.
Also, desaturating a bit will help with the “dehydrated” look.
Also, if you’ve tracked in Mocha for the mask, you could sue the track data for a “grunge layer’, something that could be overlaid to affect the texture of the skin. One possibility is to take a high res image of dry, cracked skin and scale it appropriately and track it, then either ADD (or possibly MULTIPLY depending on the elements) it onto the plate.
If you ADD it, you’d need an adjustment layer with levels and the same tracked masks to bring the white levels back down, but an advantage here is that use of levels will also help suppress the specular highlights of the sweat.
Andrew Somers
VFX & Title Supervisor
https://www.GeneralTitles.com