Drawing/Fuses/Line effects?

There’s one little thing I’ve never understood how to do in TBS. How do you create line drawing/erasing effects with objects that can follow (i.e. spark/pencil) such as with the fuse in the beginning of this video?

https://www.youtube.com/watch?v=AcdfFiP6IJg

I’m guessing that they used a technique similar to this one:

http://connectedconcepts.net/toonboom/2007/10/using-subtractive-animation-technique.html

Essentially, this is using Duplicate Drawing + some edits to make a bunch of cells that represent the image over time. You can then add a cycle on top of it to make adjusting the timing easier.

Eric