You are going to get a lot of very different answers.
THere is no real "right" answer as there are things left to opinion.
Go to youtube and type your question there and watch a few on the subject.
BTW for now I try to flush
@near 100% milky for at least five days (DTW and coco) WITH a flushing agent which drastically cuts flush time.
The tricones will continue to mature during the flush so you end up with a small percentage (10%-ish)of amber/red trics at harvest.
A week would be better two .. meh I dunno.
Using flushing agents -for the first BIG flush at the very least- does mean PHing (here there is a lot of confusion) the water as you are interacting with the roots, breaking the bonds with nuets and salts there.
If we were only washing the pot of nuets no agent would be effective but since they are...
Flush until PPM shows the pot clear-ish of nuets and then you can just give a healthy watering daily (in coco). It's where I landed
It does improve the quality even if the chlorophyll remains as Ive had plants stay pretty green even after some serious flushing.
Watch the vids do as you see fit. Have fun