If you mean the animation here:
http://www.lostmarble.com/forum/viewtopic.php?t=1360
I just used the Freehand tool in Moho and drew. In the "Freehand options" thing at the top of the window I selected "use pen pressure", then drew using my Wacom drawing pad.
I believe one has to have a drawing pad to get the kind of line I got when I drew that. If you draw with a mouse one can´t get it (at least I can´t when I draw with the mouse).
I think I had the line width min width: 1, max width: 3 and had taper start and end checked.
Also had auto close and autofill unchecked. Auto outline was checked.
No autofill because I did not want a color in it.
If you mean the animation here:
http://www.lostmarble.com/forum/viewtopic.php?t=1374
I drew it the same way, but to make the lines wiggle around, one goes the drawing layer, double clicks on it, selects the "Vectors" tab.
Then click on "Noisy Outlines" and "animate noise".
The color was a separate layer - just shapes of color.