5 months in. how am i able to tell when plant is ready for flush?
You have a few weeks to go yet.
Wait for the pistils (white hairs) brown and recede and then begin looking at the trichomes about a week later.
Always measure trichomes on flower, and not the sugar leaves. The trichs on the sugar leaves mature faster than they do on flower.
The dark, waxy leaves on the plant tell me that it is overfed. Stop feeding the plant nitrogen for a week or 2 to let her recover.
I agree with @MidwestGuy… Wouldn’t worry about it until the pistils turn brown.
You should get a good loupe or scope. Then it depends on the effect you are hoping for.
I bought and returned a bunch of scopes until found this one and I really like it.
Make sure to look at the trichomes on the buds and not the sugar leaves.