Twilight Sparkle: The feel of a genie's tail is smooth and soft, like velvet. I found that out for myself when Nova came to my castle and we had a little fun together. Having that tail coiled around you is almost like being funnelled into a bottle.
Nova Spark: It may be smoke, but smoke can still flow in a certain direction, which allows me (and Parcly and others) to slither around poles like lamias.
(This is the July monthly reward for Nova Spark. To get your own, head over to my Patreon page and make a $5 or more pledge!)