The correct way of handling guy lines on your tent is of course just ignoring them. If your tent is properly constructed the lines usually don't tangle up and can just hang loose. Though, sometimes you just want to get those lines out of the way. I will now show you a way to roll the lines up in a way that will not tangle up when you try to unroll the line. With this method you should be able to unroll the lines using mittens as well, but you will have to use your bare hands to roll them up.
Start with loosening the guy line. You always want to store the lines as loose as possible. This makes the pitching easier.
Roll up the line making the line cross itself every turn. This makes any tangling practically impossible.
Fasten the line to itself using a double half hitch. Make the line taut. Done!
To unroll, just pull the whole knot straight out. Do not pull just in the loose end, but the whole thing. The only thing that should be left after you have pulled the knot is a small simple knot.