How do you create THIS texture?!?!?!?!?!

Instead of brushed you can make a texture and place it and free transform as as you want.

To learn how to do this you may want to watch this:

https://www.lynda.com/Illustrator-tutorials/Creating-Using-Textures-Design/178134-2.html?srchtrk=index%3a1%0alinktypeid%3a2%0aq%3aillustrator+textures%0apage%3a1%0as%3arelevance%0asa%3atrue%0aproducttypeid%3a2

I have used this style of creating and modifying textures in my personal work for years , here: Jonathan Arias

I bought Von Glitschka books in college in 2009 and doing this style of texture applications is just amazing. after a while you will want to make your own textures. Which just involves making an image into black and white, adjust the levels and make a tiff. than place that tiff as a layer mask into the shape in illustrator and adjust to your hearts content. You can repeat the same texture as many time within the mask and do blending modes to achieve blends and fades as much as you want.

I found this to be way faster than going back and forth with brushes.

Anyways, that is how i do it.

Just another Appearance idea:

I've figured out a way to make a brush with this texture, Von above has already mentioned using custom brushes and his brushes are great. I've also used the method suggested using the appearance panel with the 2 fills - 1 black and white gradient with the grain effect applied and then multiplied- however I find that it greys out the colour on the black side of the gradient.

I still haven't figured out how to make a colour transitional, grainy gradient however in Illustrator with a brush it does allow you to change one colour and have the grain fade.

1) draw a medium rectangle and fill it with the standard black & white gradient. Note: Not in appearance panel.

2) With it still selected, go to effects>sketch>graphic pen and set the stroke length to 1.

3) Then Object> Expand appearance

4) Image trace in Black and White with the settings:

Threshold- 250

Paths 90%

Noise - 3px

Check Ignore white

Expand it and you can change the colour and also turn it into a brush, by playing with the brush settings you can have it follow the direction of your stroke also. I hope this helps

In illustrator:

Vector Brush Set | GraphicRiver

Here is a tutorial by Invisible Creatures showing EXACTLY how they get this effect in AI. Pretty cool stuff, I have used this method many times and the effect is great. In this example they use simple halftone dots, but the same method can be employed using any textures you have.

Link here>>>Invisible Creature Speaks » Blog Archive » Adobe Illustrator CC Tutorial + Poster

this is was so helpful to me! I found the Sponge > Stamp method to be the best and smoothest.

I go over this in my Lynda.com course "Drawing Vector Graphics: Color and Detail" here:

http://goo.gl/s866d

Here is a set of vector graindients I created for this exact type of shading FX in Ai. You can download it here:

https://copy.com/rOF7tA96vaOQlmov

The image below shows the graindients I created in use in this vector illustration. I explain everything in my videos for Lynda.com. It's not too difficult it just takes time to do it well and involves some creative masking. If you're not worried about having a distinctly resolution independent file (vector) than taking your base art out of Ai into Photoshop and doing it there is much easier and more flexible IMO.

Von

Try EFFECTS / DISTORT / GLASS / (Frosted)  use distortion around [10], smoothness [1], scaling [50%]

This may be a larger time suck than you are willing to undertake, but the purist in me enjoys doing it this way...

Create a scan of acrylic or gouache paint strokes, and either create bitmap tifs out of them or pull them into illustrator and live trace them and then just fit them into your shapes using a clipping mask. Also using rolled ink textures works fairly well. You can find those at lostandtaken.com or just make your own.

OK . . . I am determined to destroy this topic. It's exactly the kind of thing I must know how to do . . .

No disrespect Wade, but  . . . your example totally blows, haha. Great thinking, though. I tried it after I saw your post. It almost works . . .

But I'm convinced now that this textural effect is done in Photoshop. Whether or not you want to import the created Photoshop textures into Illy and mask them to vectors, or maybe just Live Trace the texture itself, is beside the point.

What's important here is just how to get this sort of chunky, "binary" gradient.

Back to my Fourth of July poster this morning and I searched for a way to knock my high-detailed spraypaint to something more like the OP's image.

With just a little setup, here's what the Stamp filter did for me:

I'm very pleased with the results. For linear chunky gradients, one could create a tiling pattern to fill shapes with, in Illy. If you know how to use PS and Illy in conjunction this method arms you with the ability to easily achieve the OP's desired result.