Focus focus focus. Many pics before were out of focus so light traces are
not sharp. How to do? Point the torch light with light on before clicking the remote control to start the shutter release. That way, it will focus on the torch light and it will track. I have to change the focus to normal AF (option 0) in Custom Functions IV so that it will autofucus. I can't pre-focus without anything in there. AF0 works perfect in this case.
Dont repeat too many rounds. It'll suffer from blurry lines. Just draw 2 rounds to get clean lines. Big torch light is already a big light brush, so one stroke is thick enough. The light in the center will define the sharp lines (if in focus) and the surrounding light will light-shadow that sharp center line.
I got YMT's name in one shot because hers is long, so I ended up doing one stroke to finish. Turned out it's the best. Just one big stroke.