Adobe Illustrator has two great features, Gradient Mesh and custom Brushes. The problem is they don't work together, even though it would be an amazing time saver. The good news is that there is a plugin which allows you to combine the two and it's called Mesh Tormentor. Follow this quick tip tutorial and I'll show you how.
1. Install the Mesh Tormentor Plugin
First we need to download the plugin from the Mesh Tormentor site. It's very easy to install, just extract the file and double-click it. Adobe Extension Manager will come to help. Just remember to have Adobe Illustrator closed before you start!
2. Create a Base Element for the Brush
Our example will be a scale brush for this exercise. I intend on using this to create repeating elements on the body of a dragon. Draw a base shape using your favorite drawing tool. I'm using the Pen Tool (P).
Now, convert the shape to a mesh by clicking somewhere in the middle with the Mesh Tool (U).
You can change the color of every point. Do it to give the scale a 3D look. Use Direct Selection Tool (A) to select single points and Lasso Tool (Q) to select multiple points.
Here is what I'm left with. This will be the scale I wish to use in my Scatter Brush.
3. Convert the Gradient Mesh Shape to a Brush Base
Here comes the most interesting part. Open the Mesh Tormentor's window by going to Window > Mesh Tormentor.
Select your mesh and click the tool shown below. It will convert the mesh to a brush mesh grid, an inter form between mesh and "brushable" shape.
And this is what such a brush mesh grid looks like:
4. Create a New Scatter Brush
Rotate your brush mesh grid to the right position. What is right position? Imagine a straight horizontal line between left and right edge of the screen - it's like a straight stroke drawn from left to right. Now, if you place your base element in parallel to this line, you can easily guess where next element will appear. I want my scales to be placed one after another in straight line, so the brush base must be placed horizontally.
Our brush can now be made in the usual way. Open Brushes panel and click New Brush icon. Then select the Scatter Brush option.
A new window should appear. You can experiment with these options, as they're very easy to change afterwards (just double-click the brush on the list to re-open this window). The most important for us at the moment are Rotation and Spacing options. We want our scales to follow the path (hence "Rotation relative to Path") and to be squeezed a little bit (lower the Spacing for it).
Now select your brush from the list and draw whatever you want. It works just like a normal brush, you can resize it and so on. The problem is it's still made of brush mesh grid.
5. Convert the Stroke Back to Mesh
Convert the stroke back to a mesh grid (not a brush line) by going to Object > Expand Appearance.
Now just click the option from below. Voila! It's a mesh again.
6. Creating Brushes of Multiple Elements
You can also create complicated brushes to save even more time. Just use two or more meshes and select them all before creating new brush.
The process is the same for such a brush, just remember it may slow your computer down as it will be memory intensive (you're going to draw a lot of meshes at one time).
7. Creating Irregular Brushes
Sometimes you don't want your brush to be completely straight - irregularities may make your picture more interesting. To create this kind of brush just place your base element at an angle. Imagine all your elements placed one after another between left and right edge of the screen - it should help you figure it out.
8. Creating More Complicated Brushes
Of course, you don't need to keep restricted to this one simple scale - there are so many possibilities for this! Just remember, if you're a beginner when it comes to gradient mesh, use some simple shape (like rectangle) as a base before building something more complicated. If you draw a complicated shape as a path and converted it to mesh, mesh points could be placed in many surprising - thus hard to control - positions.
Congratulations! You're Done!
You've just learn't how easy it is to create a Gradient Mesh brush. This method will save your time when you'll struggle with scales, feathers, fur and hair too. The dragon from below is just one example of creative use of it. Just imagine how long it would take to place all these scales one by one!