I had a whole bunch of moisture in one of my driving headlights due to a worn seal. I was able to easily fix most of this using cat litter crystals (silica gel). I made a tube out of some material, and stapled it into shape (folded over and stapled the bottom and side) and used a funnel to pour the cat litter crystals in. The tube is around an inch in diameter in order to fit through the headlight hole. I put the cover back on the back of the headlight while it dried out.