How does one accomplish the popular looks used in the commercial world such as the Illusionists boxcover, where everything has that smooth crushed black look and the skintones look like flawless porcelain.
Also, "The departed" where he shots had that old desaturated sepia tint.
Here are some low quality reference shots if that helps
I usually start photo-look processing (for stills or video) by first applying an S-Curve to the image (Image/Adjust/Curves.. An 'S-Curve' is generated by adding a control point on the 1st and 3rd dotted columns in the graph. Than, pulling the first (left side) point down, and moving the second (right side) point up. (hope that makes sense??)
This can also be done on an adjustment layer.
This technique will add a depth and richness to the image.
Than I might try duplicating the s-curved image and using Filter/Artistic/Film Grain to get some of the white diffusion I see in you examples.
This duplicate 'diffusion effects' layer will need to masked or blended on top of your main layer, as you probably won't want this diffusion all over the image.
As far as the sepia look, I'd try using Layer/New Adjustment Layer/Color Balance. You'll want to boost the yellows, generally speaking.
For sepia effects some people like to use Duotone mode to control this effect- Image/Mode/Grayscale, than Image/Mode/Duotone.
Also, there is a tutorial at the adobe exchange for creating hi-cons (high contrast continuous tone masters) from less-than beautiful imagery. It might apply to your query.