Thanks, Bob, for the additional shortcuts.
And in my post, when I say "create a new layer," I don't mean that you need to add a empty layer first. Just select whatever the top layer is, then do ALT - merge visible. That creates the new layer with the stamp.
Another one is CTRL-ALT-Tilde. That selects pixels based on luminosity. Often you create a new layer via copy after doing that. Then you use the multipy blending mode and change opacity, followed by a hue/saturation blending layer to reduce any over saturations.