There has been some discussion in this Forum on skin-tones for Zulus,
viewtopic.php?f=2&t=22705&p=248962&hilit=zulu+skin#p248962I'd say this is worth reading through as it may provide some pointers.
An approach which I use for horses is to use layers of thinned-down acrylic over a base colour; and the base colour is considerably lighter than I want the final colour to be: so a chestnut horse may start with a base coat of a sand brown.. The same principle can apply of course to human skin.
Good quality high-pigment artists Acrylics are as good as commercially-sold model acrylics, and per 100ml a great deal cheaper, I tend to use artists acrylics for horses, and indeed to base coat most of my figures.
Skin (be it human or horse) does have a sheen , especially in heat, and I use a wash of artist's drawing ink over the layers of paint on my horses. This accentuates the folds in the body (it runs into the creases, adding to shadows) and provides a subtle shine. I find this works quite well.
Happy experimenting!
PS: I imagine that in the days of ancient Egypt you would be very aware of skin tone as a marker of race and origin. Numidians would be darker than Egyptians from the Nile Delta etc etc. Worth thinking about when you are painting these figures. They may have less 'uniform' than many, but getting the skin right is important. To ancient Egyptians, this may even have been a marker of different military units? Indeed, the artist for Zvezda who executed the box illustration seems to have reflected this: the archer is darker-skinned than his comrades-in-arms.