I watched the spot again and I’m pretty sure it’s just using masks to reveal their drawings. I noticed it’s pretty sloppy too – don’t know if that’s on purpose. They could have used an arrowhead on a motion path to reveal the edge of flourishes… And the lines drawing on in the beginning would be easy with the stroke effect, which I thought you already tried. That’s basically what that tutorial is about, except it uses the write-on effect and some scaling of the elements.