What's the difference between the Flatten brush and the Polish brush? You did explain the Trim brush but I must have miss...

What's the difference between the Flatten brush and the Polish brush? You did explain the Trim brush but I must have missed the Polish brush. Also, when you create new brushes is there an easy way to have them persist across projects? Or do you have to save them in the startup scene for that?
  • cocheret replied
    It would be nice if someone answered sometime.