Below is a series of steps to follow of how you can create a simple way of creating a grunge effect within Photoshop.

1. Create a duplicate of your background or a copy of a merged layer (command/ctrl + shift + option/alt + e).

2. Create a solid colour fill layer above the merged copy/duplicate layer. Set this layer to Colour

3. Merge both the Solid Colour Fill layer and the Duplicate Copy together.

4. Select either Normal/Multiply/Screen/Overlay/Softlight for your chosen grunge effect.

Note: If you don't want the hassle of creating the adjustment yourself, click the download link below.

SCREENSHOTS OF THE STEPS

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WHAT IS INCLUDED IN THE FREE ACTION SET?

Bleach - A bleach by-pass effect with channels
Grunge [with Multiply] - A muted grunge effect which darkens the image.
Grunge [with Screen] - A muted grunge effect which lightens the image.
Grunge [with Overlay] - A muted grunge effect which adds contrast to the image

HOW DO I INSTALL THE ACTION INTO PHOTOSHOP?

Method #1
1. Open your downloaded folder or file and navigate to the actions file. It will end in the .atn file extension.
2. Double-click the .atn file and then open Photoshop.
3. Now the set of Photoshop actions should show up in the actions panel and should be ready to use.
To access the actions panel, simply go the top bar in Photoshop and click Window > Actions. The panel should then appear somewhere within Photoshop.

*Remember to 'Enable Button Mode' (simply navigate to the drop-down menu within the Actions Panel) so that each of the actions are instantaneous*

Method # 2
1. Start this method by opening Photoshop and navigating to the drop-down menu in the Actions Panel.
2. Next click the load actions link that is highlighted in the image above.
3.Clicking the load actions button will open your folders.
4. From there navigate to the downloaded folder with the specific Photoshop actions file you have downloaded.
5. Now select the file and click Open.
6. After all this your Photoshop actions will be visible in the Actions Panel and you are ready to start using them!

Enjoy!