I, personally, don't flush nor put them through 48 hours of darkness - and I certainly don't withhold water from them in their last week! I made the mistake once of not watering for a week prior to the chop and damned near lost the entire grow as it was drying out (DYING out!) before my eyes... I delayed that chop in order to give it more water and get that moisture back into the plant... You don't want to dry an already dead and dry plant...
Good luck!