Hopefully by now you're familiar with Blending Modes.  What if I told you there was a totally different way to create a texture overlay? In this video we'll explore an often overlooked feature called "Blend-If", in which the opacity of a layer is dependent on it's grayscale value.  Sound confusing?  Don't worry.  Though this seems a bit more abstract than other painting techniques, as long as you know about grayscale values and the Histogram, you'll do just fine. Due to the technical nature of this video, I'd recommend following along in your own photoshop document.   You'll need two texture images, and here are links to the two I used from cgTexture.com: the Base metal, and a Rust overlay.

AuthorMatt Kohr