How to make grunge text. This is so simple it needs no piccies
1) Find an image. Rust images do rather well.
2) place rust image over your rasterized text.
3)on Rust layer, goto Image >> Adjustments >> Threshold.
4) Find a good balance between white and black, press enter.
5) Using wand tool, make sure contiguous is off, select either the white or the black (depending on desired results
6)on rasterized text layer, press delete.
Result: grunge text.