For females i loved the look back in the 90s where women put on the black outline around the red lipstick.
So what i do is paint up the whole lips in black. Then i use a number 0 paint brush and paint the red within that black to get that look. Much easier then trying to outline the lips. Then you can dap some white on the bottom lip for that good old fashion bright lipstick shine.
For males, its more or less upper lip is always darker then the bottom.
So to start out simple, paint both lips the bottom lip color you want. Which could be a more pinkish/brownish color. Then mix up a darker paint for the upper lip.
Then you could go into details by painting a thin line between them in a darker color, and some tiny highlights on the lips to show the wrinkles of the lip.
Hope this helps some, sorta late and im tired.
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Edit: and so tired i forgot that there was this thread already going in this section
http://www.statueforum.com/showthread.php?t=52248
