This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
This is simply a different motion to the tiresome seesaw one usually employs when films are being developed. In wetting them down previous to immersion in the developer, do not keep them in the water long enough to become limp, but remove them after a few quick dips, says Camera Craft, They will then retain some of their curling tendency, so that by taking one end in one hand and gradually lowering the film into the dish of developer and then raising it out of the dish, it will be found that the film will roll and unroll quite readily, much as one would let out or wind in a reel. This method will result in quicker development, because the roll is nearly always immersed in developer. The method necessitates using only one hand, making it possible to develop a second strip at the same time with the other. The illustration shows quite clearly just how the film will behave.
Ill: Developing Film