Here are some useful tutorials:
-Smudge (abstract)
http://www.sigtutorials.com/tutorials/abstract/abstract-smudge.html]]http://www.sigtutorials.com/tutorials/abstract/abstract-smudge.html (http://)
if you scroll down you can find a lot of examples in comments
-Some regular smudge guide
http://www.sigtutorials.com/tutorials/smudge/photoshop-smudge-tool.html (http://www.sigtutorials.com/tutorials/smudge/photoshop-smudge-tool.html)
http://www.sigtutorials.com/tutorials/smudge/warcraft-smudge-signature-tutorial.html (http://www.sigtutorials.com/tutorials/smudge/warcraft-smudge-signature-tutorial.html)
second one is cool
-Grunge for begginers
http://www.sigtutorials.com/tutorials/grunge/grunge-beginner-tutorial.html (http://www.sigtutorials.com/tutorials/grunge/grunge-beginner-tutorial.html)
-Smudge and gunge
http://www.sigtutorials.com/tutorials/grunge/smudge-signature.html (http://www.sigtutorials.com/tutorials/grunge/smudge-signature.html)
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