I'd been trying to get that to work for a couple of months, on and off, but just couldn't seem to follow the standard instructions for it (crossing arms/wrists in various ways). But Gerry suggested just doing figure 8s with both poi, and then spinning the trailing one for an extra loop (more or less), and somehow that worked. I still don't have a clear mental image of how it works, and I'm still really sloppy with it (not keeping the poi in their planes, and occasionally hitting myself in the crotch with them--ouch), but while it's going smoothly it feels totally cool, flowing fluidly, kind of like passing juggling clubs can get when everyone's in sync. And even though it's apparently one of the simplest things you can do with poi, it looks really cool too (at least when someone who knows what they're doing does it).
I think in general I'm finding it a lot easier to do poi stuff when I think about the paths that the poi travel, rather than about where my hands go. I'll have to keep that in mind next time I try to follow the complicated hand motions in the book. Though presumably if I'm disciplined about getting the hand motions right, it'll result in more control and better-looking spinning; I know, from juggling, the dangers of learning something an easier but sloppier way. Sometimes it means you have to unlearn it and start over before you can get good at it.