I extended the canvas so the composition has some more 'head room' and the woman has somewhere to look.
I used a combination of the free transform tool and the patch tool as well as the clone brush and the healing brush to create the missing pieces of the background.
step 3 of 9
I isolated the frame of the glasses from the background using the pen tool. I blurred the mask to retain the DOF effect. That, of course, resulted in some color fringing, which I fixed using the clone tool. Then I painted the specular highlights back in.
On a new layer, I placed the result on top of the 'subway' image.
step 4 of 9
First I isolated the right leg from the background and placed it just below the 'glasses' layer in the 'subway' image. Using the puppet warp tool, I aligned it with the appropriate leg of the jeans. I repeated this procedure with the left leg, except I placed this below the 'right leg' layer.
I did not have quite enough source material for the buttock and a tiny portion of the tummy, so created that using a combination of digital painting, cloning and healing.
I reconstructed the background around the legs using the clone tool.
step 6 of 9
I created an pseudo 'x-ray' effect by duplicating the background layer, putting it just below the 'glasses' layer and running the glowing edges filter on it. I set the blending mode to screen and masked out any unwanted areas.
I actually did some more stuff to enhance the effect somewhat, but the above is the main technique used.