1. Open photo
This is for when for example, it is a hot day and the sweat ruins the makeup and foundation, or they just have a bad day and have some pimples etc. You can’t avoid everything so there is Photoshop.
2. Use the Spot Healing Brush
This is a special tool that will get rid of minor blemishes like spots and pimples. Right click on the bandage icon in the tool palette to select it.
3. Set Brush Size
Keep the brush size small and brush over the parts you want smoothed out or removed. The brush will try to automatically figure out how to fill it based on the surroundings.
4. Perform High Pass Filtering
Once you are satisfied that most of the minor blemishes are removed, duplicate the layer by right clicking on the Background layer (bottom right sub-window) and click on duplicate. Then goto the filter menu and select the High Pass filter.
5. Set High Pass Layer
The filter will make your layer look like this. Change the radius to a value such that you can see some basic detail like shown below. The aim of this is to ‘effectively’ invert any value roughness in the skin and overlay it on the original to cancel them out.
6. Blur High Pass Layer
Goto the filters menu again and select Blur>Gaussian Blur. Nominally use a radius about 3x less than the radius used in the High Pass, or until you can just discern blotches in the skin.
7. Invert High Pass Layer
Invert the layer by pressing Ctrl+I or going to Image>Adjustments>Invert.
8. Change Blending Mode
Set the Blending Mode of the High Pass layer to Soft Light using the layer menu shown bottom right. This will make the skin smoother but it makes the rest of the image have an unwanted bloom effect.
9. Goto Blending Options
Right click on the layer and select Blending Options.
10. Edit Blend Grays
You will see a window with 2 sliders at the bottom. Holding down Alt, click and drag half of the markers of the [This Layer] slider like shown until you get the desired level of detail out of other facial features like the eyelashes etc.
11. Mask Skin Only
Next is to mask the skin so only it is affected by the High Pass layer. Create a mask for the layer using the Add mask button on the bottom of the Layers subwindow.
12. Define Mask Area
Invert the mask by clicking on the white rectangle next to the layer thumbnail and pressing Ctrl+I. Then using a paint brush with 100% softness, paint pure white over the parts of the face you want to smooth. This will leave the details in all other features intact while the skin is softened. And it is done. From here you can apply other effects like bloom, lens blur, or lighting to beautify the photo.