I've removed wetsanding scratches with the PC/Cyclo/hand with 3M PI-III RC 05933, and that was on pretty hard Audi clear (OE clear adjacent to a repair), so it *can* be done. Took a while though.
I wouldn't go any more aggressive than 3K unless you find you need to, and I'd consider doing the final passes with the finer grit if that happens. I'd only use Meguiar's Unigrit/Nikken or maybe Mirka (sp?) paper as 3M leaves too many random deep gouges that might not come out with a PC.
Stop wetsanding a few strokes before you think you should

Better too few than too many.
The 3M PI-II Fine Cut Rubbing Compound is still available but I don't realy like its silica-based abrasives (kill you just like asbestos unless you wear the right mask). It will remove fine wetsanding marks, but people have had poor results using it to fix scratches from 3M brand paper. Hi-Temp EC might be a good choice but that's not really an OTC product so I guess the 3M is a good choice. If you can still find some 3M PI-III RC 05933 I'd use that instead but it'll take a little longer.
I'd find an autobody/paint supply place and get the 3M stuff and the Unigrit/Nikken/Mirka paper.
Heh heh, if a rotary makes you nervous, then I'd sure be leery of wetsanding, but hey, that's just me.
And as for what somebody else did on another car- that doesn't necessarily have *anything at all* to do with how somebody else will do on a different vehicle. Just way too many variables to extrapolate like that. You can't go by what other people do under different circumstances (that's for life in general too, not just detailing

).