The best results are gotten with a technique which is usually refered to as Dodge & burn. the theory is to burn (darken) the highlights and dodge (lighten) the shadows and thus evening out the 3D appearence of the skin detail.
This can be achieved in a few different ways but the two most common is either use a 50% neutral grey layer in soft light mode. Paint with a very very faint (3-5% opacity) brush on this layer, white to dodge, black to burn. Its quite common to also have a color layer for any discoloration that may occure when the tone is different in the shadows/highlights.
The second method is to use two curve layers, one slightly raised (to lighten/dodge) and one slightly lowered (to darken/burn). The disadvantage of this is that you have to switch layers to switch between dodge and burn, but this usually means you start with one layer and finish that, darkening all the highlights for example. The big advantage is that you can adjust shadows and highlights separately.
Now this is what a professional retoucher will charge you a LOT of money for because as you may understand it takes a looooooot of time. The results however is without a doubt the best you will get and will far surpass any automatic method since the artist can make valued judgement exactly how hard to apply the modifications on every wrinkle and skin pore.
Note that this is usually done after you remove larger blemishes.
One example of this can be found at http://imaginara.tumblr.com/post/55912597/...al-about-how-to
(And since im not a professiona retoucher, it wont be perfect. It will however explain the technique