how to manage the flushing time?

8-9 weeks is just an estimation. Most strains go 1-2 weeks over the estimated flowering time. I would begin the flush when the hairs are 75%brown or more. Then it's when you check the trichomes with a magnifying glass to try and get the perfect harvest, this can be anything between 1 and 3 weeks. The worst thing to do is harvest too early, very difficult to harvest too late. 🌱👍😁

I would start my flush based off of trichomes if you have a jewelers loupe. This method makes sure you harvest on time, not early or late. If you have a loupe just monitor the trichome heads and begin flush when most have turned cloudy. If you don't have this option you can combine the beaders advice and signs from the plant "hairs mostly brown" and start your flush on that timeline. Either way you will have a wonderful harvest and learning experience... Happy growing ✌️👊