I've chosen a textured face since problems with skin areas seems to be a very common concern. This is just my method of dealing with cracks and textures that appear after scanning some very old photos. I've found that this method works better for me than most other methods I've tried. I've also found it effective on prints that have a canvas texture added, old E-surface prints and files that are just pixellated or covered with artefacts.
1. First, I open the image, desaturate if the image is black & white, and adjust my levels to an overall pleasing tone. It is at this point that the cracking usually shows up as a problem if it exists.
2. With the image enlarged, and a smaller view visible, I select a large part of the skin area with the lasso tool. The smaller view changes in real time as I make adjustments to the larger image so that I can keep track of the overall changes I'm making. (To get a smaller view, select View > New View from the dropdown menu).
3. I go to Select > Inverse to invert the lasso selection and then switch to Quick Mask Mode.
4. With the Quick Mask Mode active, I choose Gaussian Blur from the filter menu. As I adjust the slider, I can see the changes take place on the red mask. When the blur is very soft around the edges and just meets the edge of the area I want to fill, I click OK.
5. I exit Quick Mask. The selection will now be feathered in the same amount as was shown by the Quick Mask, so when I fill the area it will blend at the edges. Using the eyedropper, I select a small area of skin color to use for fill. I invert the selection again, create a new layer, and fill at about 60% (I often undo and re-fill, adjusting as necessary until the density looks right to me). I don't fill the area solidly, but allow some of the texturing to show through so that it doesn't get that "fake" look to it.
6. I continue to select and fill areas in that manner until all areas have been worked. I also save my selections just in case I need them for future use.
7. After all areas have been filled, the image is much improved but still needs to have finishing touches added.
8. I flatten the image and make a snapshot of the current state. I usually name this snapshot ORIG
9. I go to Dust & Scratches and adjust the Radius and Threshold until the spotty appearance fades but the image texture remains. This is a tricky balance to master, but by playing with the levels you will discover the easiest way to find the best settings.
10. Make another snapshot of that state and name it Dust & Scratches. Activate the ORIG snapshot and point your history brush at the Dust & Scratches snapshot
11. With your history brush set at about 20%, start painting over remaining problem areas. You may need to do the Dust & Scratches several times at different R/T settings to get the effect you desire.
12. At this point, I usually to create a new layer named PAINT and with my paintbrush set to 20% or less, I lightly paint over any remaining trouble spots. While painting, I pick up surrounding colors FREQUENTLY as if cloning. I use a med. to lg. size soft edged brush and overlap previous brush strokes slightly to help with blending.
13. Finally, I add noise to the painted layer to match the texture to the underlying layer and blur slightly. I flatten the image and adjust levels on just the repaired area if necessary by selecting with the lasso tool and using quick mask mode with gaussian blur to soften the edges. I also use the dodge and burn tools at this point if necessary to enhance shadow and highlight areas.