Hi, What's the best material to use on hairline cracks without causing too much trouble on a levelled plaster surface? I've found it extremely difficult sanding down filler and then painting for a perfect finish regardless of whether I use filler or caulk etc? P.S. I've got a hairline crack on 1 ceiling (might be wider than a hairline crack in fact) which keeps and reappearing even after applying filler/caulk several times - arghhhh! Any suggestions please???? Thanks in advance.