My winter indoor riding project is to learn to idle. Finally. It has been frustratingly hard, but I think I'm close.
I brought a 24" unicycle to my lab so I can practice for 30 minutes or so over lunch, using a wall and a lab bench for support.
I've learned that idling isn't moving the unicycle back and forth, but rather rocking the unicycle in front of, and behind, my center of gravity. Full disclosure, at this point the best I've done is 4 rocks, so I'm still very early in this process, but I think that the right sensation is one of moving my hips forward and backward under my center of gravity, which seems to be about an inch or two under my navel (or at least that's where I imagine it to be when I'm idling).
It has been uncomfortable for me to let the wheel get in front of and behind my center of gravity when I've worked so hard at normally keeping the wheel right under me. Thinking about that hip movement has been helpful. Also keeping the stroke short, learning to idle with either leg down, and letting the seat take some weight, have all been helpful thought while practicing.
But the greatest help has been working on it regularly, a half hour a day. Maybe tomorrow I'll be up to eight.