You draw the lines with a flat sable-hair brush. By placing it obliquely on the skin you get a sharp edge on one side and a fading effect on the other side. To determine which side should be sharp and which side faded, you start from the centre of the face (nose). Create a fading effect towards the outside.
If you extend sharp lines, for example by extending the naso-labial fold line downwards, this will give a negative and even rather mean effect. You draw the dark corners of the mouth in the downward direction. The sagging mouth expresses dissatisfaction.