I've rooted holiday cactus (Thanksgiving type, technically) cuttings both in water and ON soil, but haven't had as much luck putting them actually IN the soil. Harder to control the moisture level, maybe.
When I did them with soil, I laid them on the soil first and spritzed the soil and the ends with a spray bottle until roots appeared, then planted them upright. Took 1-2 weeks, I think.
This winter I tried doing it in water. I'd heard that succulents will rot instead of root if too much of the stem is submerged, so I put the cuttings in a small jar with less than an inch of water -- about 3/4 of the bottom segment was under water and that was it. Nobody rotted and as you can see, they rooted quite well! I think it took about 2 weeks.
I potted them just after I took the pictures. I bottom water all of my cuttings for at least a month or two after getting them rooted; it keeps the top of the soil a little drier, so they don't rot, and encourages them to send the roots DOWN to where the water is.