...no really, how do you do it?

If you've put in your all to sneak (which you should be if you're going to play a sneak guy on master), go crouch which activates the shadow warrior effect. That usually throws them off for me. Then I roll into a nice overlook position, wait for the dragon to engage something else, and then start taking pot shots while he hovers or lands. x3 bow damage while sneaking really helps as well.

with style?

I usully just stay at range. Worked fine so far.

Keep an eye to see when he starts his descent... As hes doing so, sprint away from him. Turn and fire arrows, and keep distance on the ground