I do it manually because of my motto 'if it looks like dust just pretend it's dust'. This goes back to spotting prints, there's dust, and then there's also also small distracting highlights that sometimes look like dust even if it's just a reflection from a tiny window in the far distance. So if there's just a speck of something that somebody else who wasn't there taking the photo could interpret as dust I remove it, because I rarely have the opportunity to explain it's just a reflection from a window.