When you flush you use enough water to fill the pot and let it drain out altogether. It is a one time thing, once you flush you let the plant go without watering until it needs it again. I suggest a moisture meter, picked one up a Lowe's for five dollars. If your soil has nutes in it already, a proper flush is needed to get the nutrients to start working. Flushing is good every once in awhile to get rid of sodium buildup in the soil. Hope this helps, peace.