Go to radio shack and buy a scope, it wil help you know the excate time to harvest. Or just go buy hairs and when they all (close) turn amber, not dead and shriveled, they be ready.
When I flush I fill pot with water until the water flows out the bottom freely and lots of it (3x the container) then I wait for 20 mins and let the water dissolve the salts in soil and around the roots. Then flush again with 2 tbs molases for every gallon of water. The Molases will keep feeding the plant the last 2 weeks. Continue to give 2 tbls of molases per gallon until 2 days from harvest. Then no water. Helps buds dry. But you don't want your soil to geo Bone dry.