I feel like walking during df helps stimulate free fatty acids and enables more lipolysis hence more fat loss. Just from what I experienced, but rest and Low activity levels are just as important. Maybe a 15 min walk would be enough
Walking helps keep the lymphatic system moving, which ultimately could make a difference between breaking a fast or not. And the fresh air does wonders. Plus walking is great for losing weight in general - I see it as a win/win no matter what with dry fasting.