A few things to note:

1-pay attention to what layer I'm on as it can be a little confusing with two different portrait layers

2-you need a font that's thick, otherwise your edit won't be as effective as the face may be too much protruding out the letter. 

3-there are multiple ways you can erase the second portrait (3:30 talk through class). Best ways are polygonal tool, eraser and magnetic lasso if your model is against a plain background.

I've read back through all your feedback and a lot of you asked for more examples so the first class is a run through with explanation and how I do everything and the second class is just a visual walk through of how I do a letter portrait with a different picture and letter. Head over to the class project to see them all.