Simple, Natural Teeth Whitening in Photoshop

Lunacore Photoshop Training - Beautify a Face tutorial (part 4/7)
Their technique uses a hue/saturation adjustment layer with a mask of only the teeth (no gums, lips, etc.)  The mask is easily made by zooming in at 300-400% and using a brush with 0 hardness.
The final steps include making the teeth whitening appear natural by setting the adjustment layer opacity to 40%.  A layer opacity set much higher than this starts to look fake.

Using their steps took 10 minutes at the very most (the longest step is making the layer mask).  Once the layer mask is created, is only a matter of making minor adjustments to the