For Enlightenment versions 17, 23 or newer (Elive 3.0 Stable), there's an integrated emodule for screen brightness, you can try to enable it, if isn't already. If it works, you can assign a keyboard hotkey and adjust the brightness using your keyboard.
For Enlightenment 16 (Elive versions 3.7.x, 3.8.x, etc...), there's no emodule, but a hotkey has already been assigned for brightness control which uses the tool brightnessctl. the system is set up to use it with the sudo privileges needed. The hotkey is a standard keyboard multimedia value for brightness, normally the key with the light-bulb or sun icon combined with the Fn key
In the case your keyboard misses this key, you can change the value to a different one by editing the bindings file.
scite ~/.e16/bindings.cfg
You can also run the "brightnessctl" command directly to see if works and changes the screen brightness.
Everything is explained in the file, search for the brightness one to see if works from a terminal and change the hotkeys to a different combination if you want to.
improvements on this howto welcome 
