Photoshop's retouching tools are probably some of its most powerful.
The Clone Stamp tool and the Healing Brush are ones that I use
constantly. I also like to make sure I retouch on a blank layer (not
the original photo), but to do that you've got to select the Sample All Layers option in the top options bar when that particular
tool is active. Then you can sample from anywhere in the photo but do
the painting (or retouching) on a blank layer.
(For more on Photoshop and layers, be sure to check out my latest book, Layers, The Complete Guide to Photoshop's Most Powerful Feature.