I don't have a website to put this tutorial on, so I'll just post it here. It's for Adobe Photoshop, but I'm sure in can be translated.
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1. First off, pick a picture to use and crop it however you like. The effect works better if the cap is a darker one, but it really doesn't matter.
I found a beautiful cap of Sara and decided to crop it like
this.
2. Duplicate the layer twice and set the blending mode to Screen for both layers.
3. Press ctrl+shift+E to merge down all existing layers. Then duplicate the background twice and set both of the blending modes to Soft Light.
4. Merge all of the layers again. Once you've done that, duplicate the background again and set it to Screen. Adjust the opacity until it doesn't look to bright. Mine is set to 20%.
5. Then go to Filter>Sharpen>Sharpen. If it looks too sharpened, click Edit>Fade Sharpen and drag the bar until it is set to your liking. I put mine to 24%.
6. Add text and any other additions you want and voila!