Another PA experience I had was on the set of Midway to Heaven. An LDS film that I think premiered just recently at the LDS film festival. We spent the morning setting up the scene. They had huge flags: (you can see some in the picture below. This is just a pic I found online to show what flags look like. They are used to deflect or diffuse light)
The black ones you can see in the photo were used here to diffuse the directly over head sunlight, and then another reflecting flag (not scene in photo) was used to bounce light horizontally making it appear as at sunset even though it was midday when the actors got on set and we started shooting. The cool thing about that shoot was Kirby Heyborne was there. I snuck a photo. I'm sure they'd be annoyed if they knew... oh well.
My task during the shoot was using a garden hose. There was a stretch of concrete in the shot that was overexposed, meaning it was too bright. So they had me use the hose to wet the concrete, bringing down its brightness without having to alter the lighting on the actors. So every few minutes they would tell me over the radio to wet the concrete.