This is a great way to add material parameters to the sequencer, but for future reference, the PP parameter most appropriate to tweak to get the scene brighter is
Exposure compensation 
I assume it’s exposed to the sequencer.
This is a great way to add material parameters to the sequencer, but for future reference, the PP parameter most appropriate to tweak to get the scene brighter is
Exposure compensation
I assume it’s exposed to the sequencer.