Hello Mate
Just finished on a curved ceiling of sorts, its for a mini supermarket (I****n food) the top portion is boarded flat, width of a 8/4 board running length ways then boarded down at an angle on both sides, its a massive ceiling about 110m2 so had to do it in sections, smoothed the corners with bonding coat first then two coated (from different mix) each section, could only manage two sections a day and to be honest would not do it again as it was a real pain, its turned out fantastic, will post photos when the whole rooms done.