My technique is to lay in an off-white color, for the eyeball, then I decide where the figure is looking, where to direct the gaze. Then I lay in the iris color, sometimes round but usually as a vertical band, and then the pupil, again, sometimes as a dot but often as a vertical band. Then I cut in my flesh colors for the upper and lower eyelids, overlaying the upper and lower edges of the eyes. If the figure is large enough, I'll add a light or two, a dot of white or off-white, to reproduce the effect of a light source reflected off the wet surface of the eye.
In large-enough scales, I would add a slightly darker shade of the eyeball color along the upper lid line, because it does cast a bit of a shadow.
Having said all that, it does take me multiple tries to get it the way I want it. I have a Maschinen Krieger figure whose face I've stripped completely, twice, because I twitched and messed up an eye. But then I just cuss, and pick up and start again.
Hope that helps, prosit!
Brad