Again, if you’re going to try to specifically focus on a facial expression then you’re probably better off just doing a bust instead of a full profile. It will save you time and allow you to do more practice with less effort, especially when you’re more or less just doing the same body profile over and over again whenever you’re focusing on the face.
 
Just consider it. As you can see if you click the hyperlinked text here there are plenty of people who do the same thing that I’m suggesting to you, if you need an example.