Here's a easy fast way to apply texture to your artwork:
Open the texture in Photoshop, drag it onto your artwork using the arrow button.
Using 'Free Transform' you can make it fill the whole image to the size you need- (Make sure it's already close to the same size as your image- if it's too small of a file and you blow it up, it will just look pixelated and yucky).
Go to the 'Layers' tab and right where it says "normal" click the arrow next to it and you'll see a selection of options to choose from-
I like to choose "Overlay" most of the time (sometimes "multiply")
Up to the right where it says "opacity" change it anywhere between 20%-65%- depending on what looks and feels right to you. Just make sure to "keep it real" if you know what I mean.
Tomorrow I'll share another texture and some tips on applying it to the actual brush itself.
Click the image for the full size:
Have fun! :)