Work with the Smudge tool

Select the Smudge tool   (R) from the toolbar. If you can't find the Smudge tool, click and hold the Blur tool (  ) to show the other related tools, and then select the Smudge tool.

Choose a brush tip and and blend mode options in the options bar. 

Select Sample All Layers in the options bar to smudge using color data from all visible layers. Deselect the option to only use colors from the active layer.

Select Finger Painting in the options bar to smudge using the foreground color at the beginning of each stroke. Deselect Finger Painting to use the color under the pointer at the beginning of each stroke.

Click and drag in the image to smudge the pixels.