The following applies to this specific example: The scar has been made using Derma Wax.
Use the convex rounded side of the Derma Wax Spatula to take Derma Wax out of the jar. By scraping it out, you already make the texture a bit flexible.
You then make the wax easier to model by applying it to the ball of your thumb and scraping it off again with the spatula two or three times. The wax must be flexible but also firm and must definitely not be allowed to get too soft and sticky.
