[ Thanks to Michael for this link.
]
“This is a very simple method to making photographs
grungy, but its also a good technique to have handy in your mind
for any post-processing you might do in the future!“1. Hard Light Blend
* Open your photo up in GIMP
* Duplicate Layer
* Set `Mode’ `Blend’ to Hard Light (OPTIONAL: make them both Hard
Light and move up the Original layer, might be slightly better
quality later on!)”