Paintbrush overlay question

[michaelbr]

I'm trying to do something similar to this video (5:45 explains how to use overlay in paintbrush), I could follow/duplicate until paintbrush overlay, then I got lost (the paintbrush on the video is bigger than the stroke of the pen, but when passed over the pen stroke, it only enhanced the color of the stroke, not the transparent background, in my case, the brush painted over the width of the brush, not only the pen stroke), what am I missing?
ps: the opacity is set to 100% in both cases, if I tried to set mine to 10%, it won't enhance the pen strokes.

Thanks for your comment/suggestions