i dont flush per say but last week i give only small amount of base nute plus carbs/sugar and last watering or 2 just straight ro water
thats always what i considered flushing. but i guess peoplr running swimming pools through their pots to try to flush it out. bad idea in soil or promix as you really dont want to drown roots. the last weeks the plant will drink alot less and youll notice you dont have to water as often/much