See (there was a url link here which no longer exists) for a recent discussion of "twiggle" ("twirl" in that thread) stick agitation generally. If you already use this agitation method, then you probably won't get a lot out of that thread; however, if you're just starting out with that method or with developing generally, you may pick up some useful tips. My first attempt was a disaster (hence my starting that thread), but my next two attempts produced fine results. AFAIK, there's nothing special about Diafine in terms of agitation methods, but I've also never used Diafine myself.
Concerning rotation direction, my first attempt rotated only clockwise and produced poor results. My next two rolls I did more vigorously and in both directions and that worked fine. Perhaps just counter-clockwise would work, too, but I haven't tried that. I think I'll stick with the both-directions approach, since I now know that works for me.