Dirt, a reflector doesn't need to be shiny. Something as simple as a white piece of paper is all that is needed. If placed below the subject it would remove some of the dark shadows, giving more details in the darks, essentially giving the impression of softer light. The risk of course is that if too much light is reflected one would end up with a very flat uninteresting light instead, making things worse, instead of better. This can happen real easy... Here I think only very little reflected light would be needed as the light is already pretty good
.
