If he hadn't had to keep one hand, one finger, on the duster to control the charge, both of them would have been running down her spine to grip that exposed ass as she went down on him. As it was, just the one hand was holding on as he leaned half over her and quietly thanked the Lord his reformed Catholic heart wanted to believe in for women as nimble and willing as she was.
Just as long as she didn't stay down there too long. A rubber was good for going in the bottom end, but was pointless for a blow job. He didn't think she'd let her tongue do the walking for terribly long, her back now exposed to the chill that his arms couldn't protect her from in their current position meant she'd likely be back on her back in no time. Sometimes the cold was the best encouragement.