m0useanswered grow question 3 years ago base your flush on your trichome indicators, then you will do this 1 week or 2 weeks before harvest depending on your medium and feeding style. 1 week is usually enough. personalty though, I do not flush. but that's the method if you do.
10-30% amber is ideal for most growers for harvest. I prefer closer to 10%, basing readiness on Pistils is not the best as they can dry up from light or lack of humidity.
a visual for reference.
https://aws1.discourse-cdn.com/growingmarijuana/original/3X/2/b/2b2655fe5f3346339f83bffb081292e6612d3812.jpeg
Good Luck and Happy Growing