Tool Used: Adobe Photoshop
Step 1: Prepare Face
Darken image with the burn tool where desired, e.g. on the eyes, mouth and perhaps clothing.
Step 2: Eyes
When this is selected copy the selection and paste it on a new layer. Move the new layer to the selection's original position if it has moved.
Apply a Filter => Blur => Gaussian Blur to the new layer. The new layer should look like a blurry, gray almond. To make it black, apply FX => Color Overlay to the new layer and set the overlay to black. Reduce the opacity of the new layer if desired.
Now, on the layer that we copied the eye from, use the burn tool to darken and fade the image into the new layer. This setup gives you a lot of choices. I decided to make the new "eyes" of Abe slightly lower than his original ones.
Now do the same for the other eye. Bend the eyebrows to your desired shape using the smudge tool with a 50 - 90 % intensity.
Step 3: Creepify the Eye
Step 4: The Place That Is Most Feared
Now scale it to desired width and height. Erase the edges of the new mouth image until no edges are visible. With the mouth arranged in the perfect place, select its layer and click Image => Adjustments => Hue/Saturation. Change the brightness until the mouth's skin matches your photo.
Now if the mouth is too dark for you, brighten it by Image => Adjustments => Brightness/Contrast (lowering contrast, not changing brightness). Also use Image => Adjustments => Replace Color to replace black with gray.
If the face looks out of balance, consider flipping the mouth with Edit => Purge => Flip Horizontal. Otherwise, just play around with the smudge tool to balance out the nose.
Step 5: FX & Finished Mouth
1.Dye image red : Click on the black and white semi-circle in the lower layer panel. A combobox should be displayed. Click Photo Filter and check Preserve Luminosity. Now select your color. A new effect layer will be added: place this at the top of your layers.
2.Invert image : Click on the black and white semi-circle in the lower layer panel. A combobox should be displayed. Click Invert. A new effect layer will be added: place this at the top of your layers.