I've shot a few barn weddings; IMO they're a nightmare to light. There's limited bounce surface, and constantly and dramatically changing ambient light. This weekend I set up a few speed lights (with CTO) and had to change up my strategy as the light changed. Started the reception with gridded flashes pointed directly at the subject because of the strong back-light. Later was able to bounce a couple flashes off the ceiling decorations, and then for the dancing move a couple flashes as kickers for the dance floor. Was able to keep a pretty consistent look throughout the evening, let me know if you have any suggestions!