Trichome is your best bet if you don’t know how to “feel” for a ripened bud.
Breeders will ultimately have the fastest POSSIBLE flowering time listed to help sell there seeds. If you go an extra week to breeder recommendations you should be in the right ball park.
Most people say a jewellers loupe is how they check. I bought one and I’m returning it. Can’t get a good enough look through the 60x to really tell. It’s a pain to get a good look and you need to check the plant as a whole really.
I just invested in a USB microscope and it’s key.
Happy growing