Dro, wait until the hairs are turning brown faster than they are being replaced with fresh white ones, like 90% brown, and then start looking at trichs with a magnifyer.
If you don't have one, squint. hahahaha just kidding.
The plant will have a sparkly look to it when the trichs are still clear. Go see how it appears now. It should sparkle a little in bright light. When it looks more misty/frosty there's your trichs going milky. Your harvest window will start soon after you notice that. But you really need a magnifyer to nail it down.