My favorite is to use clone, select a soft airbrush, set the brush / clone tool to "Lighten", 50% opacity.
Sample nearby wrinkle-free area, then clone over wrinkle. It lightens pixels darker than the sampled area (i.e., the shadowed wrinkle), but at 50%. I find the results very smooth and realistic, as it simply softens rather than eliminating the wrinkles entirely.
Do it on a separate layer, then turn that layer on and off to see the amazing difference.
Good luck.




