This is a tricky shot to composite and may seek advice at a later stage on how to tackle it more realisticly, but as the light is moving around a lot from the source and is from behind the text I backlit it with a very strong light to keep the front of the type in almost total darkness and added some random exposure in after effects to make the lighting of the type flicker a little to add some sens that the light dancing around it in the footage was affecting it.