I've seen the striping that Phoenix does before, she's rather good. Having only done a little so far I'm not going to show you all just yet.
I've spent the last 20 years as a graphic artist using both ink, paint, brushes and of course a macintosh, and the best advice for a would be striper is to 'look where you are going'. Having started pulling a line, look beyond the brush to where you intend to finish. That helps with getting your line where you want it. Ask any motorcyclist, look for the point you wish to arrive at, and you'll get there!