That's pretty much exactly how I would do it to except I just paint on the Adjustment Layer Masks instead of making a selection (Easier if you have a tablet, not so with a mouse)

I think the blind feathering kind of hurt the image though; your teeth sort of have a haze now. Maybe select less feathering, adjust with the smudge tool or try using a soft brush to select. Also if you just left the lightness alone in the HSB dialogue and used only the levels to adjust the brightness I think you'd get better results.

You have an excellent video voice, it's very eloquent and understandable.