Defining the character’s lips
The lips are the most difficult thing to get right on the face. Once the teeth form is established, I build the lip forms up aggressively. I then create the clean separation on the lower lip line, and the centre crease between the lips. I use the Pinch brush to squeeze the lower lip line into position. I like to go over this several times with the Pinch brush until the lip becomes well defined. I use a custom-made Mech brush to create the centre separation line. I also use the Mask tool to isolate forms for more specific form delineation (hold down Ctrl and draw on the form to create a mask).
Pinch brush defines the lip line. Use a mask with the Mech brush.