Not everything I know about power sanding is wrong, but based on the evidence (the occasional swirl mark) some of it is. At least now I know the fix, having just watched a video Gary Katz shot while visiting Festool’s U.S. headquarters in Indiana. It’s of a demonstration Larry Smith (a manufacturer's rep for Festool) performs at the Katz Roadshow.
In his post about the video on This is Carpentry Katz goes out of his way to say don’t read the story “If you are sensitive about articles that seem to favor a particular manufacturer”. Smith works for Festool so of course he dwells on that company's products, but much of what he has to say—in terms of technique—would apply to any brand of sander.
What I learned from the video is that when I’m in a hurry I tend to push too hard instead of letting the tool do the work. I already knew not to skip grits at the low end. Smith has a cool way of demonstrating random orbital action, and why it is you get swirl marks when you push too hard.
He goes on from there to show what a Rotex sander—with its geared rotary orbital action—can do. This is probably the part Katz was concerned about, because it’s a bit of a sales pitch. But it’s an honest one. I know because I bought a Rotex (the 5" model, not the 6" model in the video) a couple of years back and it does pretty much everything Smith says it does. The one thing I'm not sure of is his claim that the Rotex removes stock four times faster than a belt sander. It definitely removes stock faster, but I can't put a number to it because I haven't run the tools side-by-side. Smith is certainly correct in saying it's possible to collect virtually all of the dust when using a Rotex and that the tool is capable (when switched to random orbit mode) of producing a very fine finish.
It's a pricey sander (I paid around $460 for mine) but for me it has been worth it because it does the work faster and greatly reduces the amount of time I spend cleaning up dust.