If you are using the Pro edition or the Trial edition (the same thing), you can use a Glyph Transformation to do this in one step. Tools, Glyph Transformations, and click the Open folder icon. There are several different Thin Transformations to choose from. They may need adjusting to suit your font’s design as they were designed for one particular Sans Serif typeface.
See my tutorials on Working With Transformations and
If your font has high contrast between thick and thin strokes, it is quite difficult — otherwsie, it generally works well without much adjustment.