That’s the way to do it — I don’t think there’s any easier way.
Experiment with some simple glyphs to check your transform values.
Copy the glyph to the clipboard, and paste it back after performing the transform, then undo the paste while you’re testing the transformation because there is no undo for transformations.
When you have figured out the desired combination of scale and thin, select all of the glyphs in the overview that you want to transform, and apply the same transform to them all at once.
This Tutorial may help.