As you have already found out, Canon off camera flash is not as easy as the Nikon way.
The Canon built-in flash has no facility to control a flash off the camera, unless you use a digital slave trigger. This means you have to use flash in manual mode, which means the automatic part you ask for is not possible.
The ST-E2 controller sits in the hot shoe, and that means the built-in flash will not work.
To get the camera to do most of the work, you have to use two flash guns. The camera mounted unit has to be a master, which means a 550EX/580EX/580EXII if you want to stay Canon. The slave can be one or more of those, or a 420EX/430EX. This allows full E-TTL II metering, so everything is basically automatic.
The Sigma 500 series is another option, and it
may work off the built-in flash. Don't quote me on that... There are other, less expensive auto thyristor units that claim to sync off of the built in flash, by makers such as Sunpak and Phoenix. They are also less expensive than the Canon units.
I use a 580EXII on the camera and a 580EX as a slave. This arrangement works well, once you understand what the two flashes are doing.
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Crime Scene Photography
A small gallery of personal work:
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