Lips step by step ( detail guide below )

   
    1 :  use color 1 with multiply mode brush draw a basic shape of lips

    2 :  use color 1 with brush , put on some color to the lips. dont worry if you smudge the line, we'll fix it later

    3 :  use color 1 with water (or blur ) blur em color out. then use erase to make a clean edge

          use color 1 with multiply mode brush redraw the line 

    4 : use color 1 to shade the shadow under the lower lip, use color 3 to color the teeth and highligh the lower lip

    5 : use color 2 & 4 with vivid mode brush put more shade on the lips

    6 : use color 3 to highlight stuff

         add the glossy effect by using dirt 9 brush on a new addition layer

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lol sorry for the bad english .