Honestly, I have done it both ways. I have found that it's better to just spool it in a clean as you can. As long as you put enough weight on it to put the line under tension, it works fine.
I use a slightly sloped parking lot, light pole, tree saver and an extra person in the car when I re-spool my line. I use the weight of the vehicle being pulled up hill in neutral. It has worked great every time. The second person just sits in the drivers seat in case something bad happens and the vehicle starts to roll back. I do it at night and have only been questioned once.