How To Paint Lips

Ever wanted to know how to paint sexy lips?
Here's my approach on it:

Paint with the thought of just adding in shapes.

Paint the second shape of the lip but with a separating line where it and the top lip are touching.

Paint the values: Inside the mouth is the darkest, and remember the light is coming from above. Lips are curvy, so curve towards the shadow with darker values of, in this case, pink/red.

Paint more on what you see by rendering the colors together more sharply on areas that are quickly going from light to dark [shaded areas indicate depth/space].

Paint in more teeth as you paint more depth. The more you add shadows the longer/more projected the lips will appear.

Paint in some lip gloss! [Adding white very delicately helps create more depth for the viewer. Increasing that realistic value to it, especially if what you're painting is naturally capable of being reflective]

Enjoy! :)