30' streamer and 20' leader.
You can use a tool made of an bolt (1/4-20 and as long as you can find with threads all the way to the head) thru a piece of ply that is about 8" long and two pegs about 6" apart (3" on either side of the bolt. The bolt sticking thru opposite side of the ply as the pegs are out of. The bolt can then be put in a drill and used as a winder. You can then count the turns to get the number of feet needed and several can be given to YOUR HELPERS.

The streamers can then easily be pulled off the winder and a rubber band used to secure them.

I have been to meets that the leaders were already tied and those that the leaders were not already tied. there seemed no difference in the number of lost streamers (none) so it is your choice and not guilt trips required.

As a fast rule of thumb the average arm spam of a man is 6' so five arm spans on the streamer and three on the leader and you wont see any difference in the air.

Take care Jim