I use a LED 30x 60x eye loupe. its not easy! what works best for me is to cut a piece of bud that you suspect being ready. Cut it off and take it into some natural light so you can give it a good evaluation. What im looking for is mostly cloudy (80%-90%) with a bit of amber. Clear trichomes arent ripe. You want to look at the bud itself and not the leaf. And check the whole plant overall. Reading trichs is kinda an art and you get better with experience

Also, all though a few of my weedportal members may disagree,    If you start your counting upon first seeing flower, you will be very close to the breeders flower time