EXACTLY!! Final rinse from the top....A LOT (final phase nutes?). drain tubs, add fresh and flush till the end my friend.On my flood table.
I like to leave the res about 10 litres shy of water. The I add the Ph Balanced 10 liters of H2O over the rockwool wool using a watering can (do it gentle as to not hurt the roots). A reverse flush, if you will.
Then a couple of days of regular timed floods with Ph'd water.