Using the Rubber Stamp
The Rubber Stamp and the Style Brush share a spot on the toolbar. Click and hold on the one tool to switch to the other.
The Rubber Stamp tool allows you to quickly and easily fill your document with duplicates of the same graphic (or of a group of graphics).

The first time you switch to the Rubber Stamp tool, the mouse cursor will look like this:
Click one of the graphics in your document to "pick it up" for stamping, and the cursor will change to look like this:

Then click anywhere in the document to create a duplicate of the shape you "picked up". Keep clicking to create as many duplicates as you want.

To change which graphic is duplicated with the Rubber Stamp tool, hold the Option key (the cursor will change back to "pick up" mode) and click on another graphic in the document.