Sharon Schamber has wonderful video tutorials on doing bindings and the corners. I also love Missouri Quilt Co tutorials. These 2 sites have very clear easy to understand tutorials. How I learned was to have the videos continually playing while I am on the machine learning the techniques. It is easier to 'Learn by Doing'.
Good luck, and once you master this to your satisfaction, you will enjoy it!
And is it possible the lady who doesn't like your sizing of the article, show you exactly what she wants and expects? I do understand your concerns completely. I make the hats too.