I might make one to help people out though my knowlage of it is still basic. But perhaps that is just the kind of tutorial most people need when first using it cause it can be frustrating very fast. How I learned it was I told myself one day, I drew a not so detailed headshot of one of my characters and told myself I was not to exit out of the picture. After watching a few tutorials on youtube I went at it. My first picture took a long time to complete but over time it has become second nature and it is much easier. So my suggestion is look for good youtube tutorials as they really SHOW you how to do it. And be stubborn with yourself and practice. Within a few pictures you will feel a lot better at using it.
I wish you luck. I will see if I can get a tutorial done in the next few days that may help out. If I do I will share the link here for you. 
