This is what I did years ago:
This is all I've managed since yesterday:
Seems I have forgotten how I did this a couple years back. I'm using PP. I can't smooth those edges as much as I need to.
I thought all I had to do was repeatedly apply the Remove Noise effect, up to a dozen times or so. Whatever I did, I clearly remember that I saw the edges smooth out a bit more every time I applied the effect. EVERY TIME. I would stop when I thought the edges smooth enough for a kid to trace accurately.
Now, the edges smooth a bit the first couple times I apply the effect, but I reach a point at which the effect no longer works and these edges do not smooth any more. The smallest floating blobs do not disappear the way they did before. No normal kid could trace shapes as complex as those in the second image.
I can do something similar by using the Smooth effect several times, and then applying the Posterize transformation again, but I really do not remember doing it that way before. I don't remember a blurriness being part of the process. I could swear all I did was Remove Noise repeatedly, but maybe I'm not remembering clearly. It has been three years.
If you could reverse engineer what I did three years ago, I'd greatly appreciate it.
I've not tried PowerTrace. I swear I repeated an effect and watched the outlines smooth out gradually, a little more with each repetition, and stopped when I figured a kid could trace the outlines. But I absolutely cannot recreate the process as I remember it. The Smooth effects work in a manner I described, but you have to apply Posterize to remove blurriness. I'm settling for Correction: Dust and Scratch this year. I don't understand the relationship between Threshold and Radius very well, but the process is fast and can be highly reductive. I bottom out Threshold and set Radius to 9; this does well enough.
It's Dust and Scratch. It has to be applied through the menu, though—not with the Repeat shortcut (CTRL-F). It will not work with CRTL-F. Repeatedly applying the Dust and Scratch effect through the menu causes a gradual smoothing of the outlines as I described. I'm not sure where the Remove Noise effect came in, but perhaps to remove the smallest "debris" after Posterizing an image. The shortcut keys in X5 are a mess, with multiple menu items sharing the same shortcut (Combine Channels and Corection both use "O"). I remember doing something to fix this once upon a time, but cannot remember the process now. I've Googled it without success. I bring this up, because I used to use the shortcut keys to repeatedly apply the effect. The sharing of shortcut keys between menu items now makes this bothersome.