hi i have had conflicting advise about how to repaint my exterior windows i have been told to remove and sand down flakey paint then only use undercoat then a top coat of gloss i have asked if priming the sanded surfaces is necessary and been told no as it was already primed some timber ie the sills i have completeley sanded back i am also getting a painter in to do all the high timber eaves etc etc and want the job done correctly so primer or no primer? cheers