How to...pen drawing effect

Just wondering if anyone knows of a good tutorial on how to make animated lines as if they were being draw with a pen.

Here’s the desired effect I want however this method leaves a lot to be desired in terms of file size.

Note: For the effect I’m creating I’ll only be drawing lines (no fill, unlike the flashkit tutorial above). Also, there are quite a few curving lines.

Any help on this subject will be greatly appreciated.