Masking in After Effects

We were working on after effects yesterday, mainly using the masking tool to make a lighsaber.
To begin, we downloaded another groups short clip where someone leaps towards someone else with a lightsaber, our job was to add the effect to the saber, so it actually resembled those from the Star Wars trilogy.

 I imported the video to After Effects and created a new composition, then I went to the layer tab and created a new solid, making the colour white. I then used the pen tool to trace around the lightsaber in the first frame and clicked the stopwatch icon to create a keyframe.

Clicking the stopwatch creates a keyframe, which allows me to change the shape of the pen tool on each frame, if you don't create the keyframe then the shape of the pen tool will not change on every frame. I made this mistake on my first attempt and had to re-do 25 minutes of work.

You now reach the time consuming part, changing the pen tool on every frame. It's not difficult at all and is hard to mess up, just trace the lightsabers movements.

When you reach the last frame you should have a white box that moves around like a lightsaber, but looks nothing like one. Make 3 more layers of the mask and feather each one more than the last, for example, the first should have 20% feather, the second 40%, and so on. add a bold colour to each layer and you should have this effect.