Youtube has tons of classes for this sort of stuff. Typically it's just going to be brushes in Photoshop. Illustrator will be a tad harder to create this kind of stuff.
To make it simple. Take some paint, splatter it on a contrasting medium, take a good hi-res picture, and then trace it in Flexi or Live Trace it and make vector shapes. Layer with multiple different versions of the splatter. Add some gradients. Do the same thing but with rust pictures, and layer that in. You'd end up with something very similar and it'd be your own.