Tricky step #1. Use the composite transform to subtract out what will be the top layer
of text above the shadow. The input image on the composite transform is the blurred drop-shadow,
the overlay image is the mask that was used to create the blurred image. Note that
the compositing operation is subtract, and we move the top text layer up and to the left
by a pixel or so, using a 1-point alignment method. When this transform is set,
just "Apply", do not click "OK", because we will use it again in the next step.