I agree with Bruce, I tend not to try and get down to 'whites of their eyes' detail - I have tried before, but it kind of makes them look a bit like something out of 'The Shining' ("Heeeeeere's Johnny!"). So these days I just apply a thin wash of a darker flesh tone to eye sockets, and under the nose and chin, followed by a dry-brushed lighter tone to the high-spots like the bridge of the nose and the cheek-bones if they're defined well enough.
In terms of making my own figures, I've tried Chris Walas' method and I just can't get to grips with it - so instead I make mine from hacking up bits of 'Preiser' figures and putting them back together, filling the gaps, adding extra details then finally painting.
I have a website which has recently been updated with my method for 'sculpting' figures - although I guess technically it's not really sculpting.
My preference is, if the eyes are wide open do the whites of their eyes. If they are squinting don't. Only remember, the whites aren't white at all, they are sometimes a light, light tan or pinkish, or folks with bad livers, like bumbs and whinos are more brownish and yellow, and as Bruce pointed out, it depends on how close someones gona get.
That being said, when I do the whites or any eyes, I start with whites, do the iris, do the pupil then the eye lashes (if that person has any) then dark areas around the eyes (they are sometimes a bluish or purplish color depending on complexion) then blend in the rest of the face. Faces are not all one color. Even people of color have lighter and darker areas within a 1 square inch area of skin. Areas around cheek bones, chins, brows and foreheads, tend to be lighter because the skin is stretched across it. Heavily wrinkled faces have subtle splashes of red blush in the creases of their wrinkles. Older people have rougher more darker and lighter spots. Dark skin people have some olive splotches here and there and even a little blush in areas around the cheeks nose and lips.
Best thing to do is find a fellow human who doesn't mind you examinging their skin real close and set down and have a good long look at their face and take note of all the subtle color variations.
Note that Aunt Joan has whites to her eyes, but they are so close to the color of her skin, you can hardly see them
Kai`ulani's whites are more visible because she is darker, but note they are not white, but pinkish tan.
What about the face color? Do you apply multiple layers of color or washes, or just find a good single color and go with that?
I use Patio Paints, Apple Barrel, etc. They have a couple shades of flesh/pink and I tyically use these mixed with a little tan/light-medium brown so everyone ends up looking a little different. African Americans are obviously brown-black. The flesh is such a small area that I mix it up what I need and apply it in one coat with a small brush, almost "dry-brushing" it so as not to loose the features. (The outdoor paints are very thick/gloppy.)