Hey @forums2012,
Keyboard Maestro can increment the increase or decrease in brightness of the main screen, but I believe that's it.
If you want more control then you'll have to resort to scripting, and you'll have to use a 3rd party utility.p
In this case the brightness command line utility looks like the best option.
It can be installed with either MacPorts or Homebrew.
Here are fairly detailed instructions on installing Homebrew and then using it to install apps:
Installing a Unix executable with Homebrew
I use MacPorts instead of Homebrew (although I think hb is easier for most folks to manage), and I installed the brightness command line app with it.
It works perfectly on my Mid-2010 17" MacBook Pro, but I don't currently have a multi-monitor setup to test secondary monitors with.
That said I see no reason offhand why brightness would fail to work with them.
-Chris