if you snip the top off a bud (thats the most ready part) and leave some of the budstructure left, it will regenerate.
small bud should dry in 2 days (depending on humidity) but you can use the oven on low if you are in a hurry (or anything warm to hot)
you can sorta go by the hairs, but some strains will get brown hairs, then keep on growing new white ones so a week later its completely white again.
others will have brown hairs when they are ready, so you sorta cant either go by the hairs too lol. (not the first time you grow a strain)
i find the testsmoke better than using a microscope, if havent smoked the strain anyway, i wont know if i like it best with clear/cloudy or amber trichomes to begin with.
if you got some popcorn on the bottom, you could testsmoke that too, but just remember the popcorn isnt as mature as the top. not if it didnt get any or little light, so its better to testsmoke the actual buds, just pick the smaller ones and you can leave a little bit left of them to regenerate, just in case you need to flower longer.