and its already set to grey scale. but if your using your own icon make sure you set it to grey scale, and it needs to be fairly light. so if its to dark go to Adjust >> BRightnes & Contrast >> brightness and contrast and match your settings
Brightness: 33
Contrast: 7
OR you just fool around with it.
Once you've done that take THIS texture from INSTANTROCK.com
and set it to overlay at 100%
Now take the colored version of the little duck and set it to OVerlay at 100%
Now, this image wasnt so vibrant with colors, if your using your own then just add this next step.
Take the image and go to Adjust >> Hue & Saturation >> Hue/Saturation/Lightness and set the settings to mine
Hue: 0
Saturation: 35
Lightness: 0
Then lastly, take this texture, again from INSTANTROCK.com set it to lighten at 100%
Now you can add text or brushes, although its not recomended.
! C L I C K for my final result!