He and i also said..dont flush.. none. Its not needed.
You might want to flush ..IF..you grossly overfed and burnt the plant.. this can stop further damage but otherwise its pointless.
Trust me, i did it for ages and believed it was needed..lately no and ive learned it doesnt make a difference.
Now the thing is you CAN give just water for the last week or 2. Then the leafs will all start fading and dying. BUT the problem is if you mistime it , and need 2 weeks more for instance ,then youre screwed. Just keep the plant healthy start to finish. Maybe give a pure water feed when you know its definitely done