The fundamental divide between illustration programs that are vector driven (like Illustrator) and raster driven (like Photoshop) is one of control over elements. In Illustrator, everything you draw is defined by Postscript attributes, where lines have a stroke, a color, and an enclosure of lines has a fill. In a raster program, a shape is defined as an X-Y coordinate with a mix of colors in a color model. What’s a vendor to do when it’s defined this divide? Try to remove it. This is why Photoshop now has some limited vector drawing tools, and why Illustrator now has custom brushes and symbol painters. However, the way that Illustrator handles brushes (and the fact that they’re named brushes at all) is, in many ways, disingenuous. When you tell a graphic artist “You’ll be drawing with a brush”, you give a set of expectations about behavior – how the bristles will splay, how the ink will run…and that set of expectations is completely inadequate for Illustrator brushes.additional reading
Illustrator brushes decorate a path (the basic line segment that everything in Illustrator is built to manipulate) with other effects. What this means is that while it’s *possible* to paint with a brush tool in Illustrator, in most cases, you’ll be using the brush tool to apply a special effect to a line segment or path. This can be confusing at first, but is much more flexible. The basic brush effects in Illustrator start with two that are analogs to how Photoshop brushes work – they’re the basic art brush and calligraphic brush effects. What’s nice about them is that you can draw your basic structure into place with line segments and the experiment with different brush effects. You can then save the presets on those brush effects to use later.
This separation between the drawing stage and the application of brush effects allows for things that are much more flexible than mere ‘painting effects’. Rather than have brushes that define the smearing of colors along fake bristle patterns and pressure patterns, you can change brushes to display sprays and spreads of symbols and other pieces of vector artwork, like painting patterns along the line of a path, or a brush that paints perfectly replicated arrows or flowers or ladybugs along a vector path.
When you adjust the path, the attributes of the symbols and brush strokes flow along with the changes, and scale automatically. What this means is that by learning these tools (and they’re not always easy to wrap your head around) you can speed up the creation of very intricate artwork with repetitive elements. The best way to learn about this is to experiment with it; Illustrator comes with an amazing library of pre-sets to play with, and then you can tweak them as you experiment. As you go along, you’ll discover that many things you were doing with cut and paste and the pathfinder tools can be automated (and be made much more flexible) through use of the brush and symbol tools.