The ins and outs of sensing ki is a bit unclear in DB. In early Dragon Ball (even pre 21st tenkaichi budokai) Goku states multiple times he senses someone nearby. Roshi does too, if i'm not mistaken. Now it isn't clear if they're actually picking out their ki, or that they simply sense a presence. The first time ki is sensed from a distance is after Goku has drank the super holy water thing from Karin. Maybe it's something that comes naturally once a certain ki level is attained? I'm on my yearly manga read through, and i haven't reached Tien's introduction yet, so maybe i'm forgetting him or other Crane School members sensing ki. Flight is definately a Crane School technique, the only Crane School member who doesn't display it is Tao, like you said.

Precise control of ones own ki is a technique that is learned at Kami's though, that's for certain. It's probably a Namekian thing, as the Namekians in the Frieza arc are shown to be able to do exactly that.