How to HAC in 3 Step. Not an IKEA Hack but HAC- Highlight and Contour for your face. Its quick and easy. You’ll never want to stop! How to HAC. First off, If you have never heard of HAC’ing don’t feel out of the loop. Before I started wearing Maskcara years ago I had never even heard of the term. HAC stands for Highlight and Contour. The purpose of HAC’ing is to create dimension of the face by using different colors. Using the principles of light and darkness to create a 3 dimensional face.