Okay! I finished up the v3 application. The skis actually ended up sitting in full sunlight for about four hours total, since my partner and I were watching a movie.
I don't know if I'd agree with the guide's description of the residue as "chalky white", but there definitely was residue. In the picture below, the ski on the left has been "brushed" and the ski on the right has not:
View attachment 13421
And the below image is after both skis have been "polished".
View attachment 13422
The instructions mentioned needing to pay careful attention to residue on colored or clear areas of the base and that definitely seemed to be the case. I could see areas needing attention pretty clearly on the black areas of the base but had to bend down to see how the light reflected off the surface for the colored areas.
The tips and tails were a bit more difficult to "brush down" than the other areas, although someone with a more secure workbench and a rotary brush might have an easier time. The edges were also a little bit of a pain—it felt like the bristles weren't really reaching properly. Again, a rotary brush would likely be handy here.
Overall, the process was pretty straightforward, and I was glad to be able to take advantage of a rare unambiguously sunny San Francisco day.