I have explained that a bit earlier.
http://www.facialforum.net/showthrea...l=1#post724622
http://www.facialforum.net/attachmen...8&d=1376466523
I never use the *sharpen* filter in Photoshop. I am mainly using the highpass filter technique or an other one where you use multiple layers of unsharp mask on top of each other.