High weefi,
You do NOT need to use 48 hrs of dark period before harvest. This does not bring any benefit for your plants. You will only lose 24 hours of photosynthesis to make those buds a little fatter and juicy.
Yes when you want a head high without body focussed you should harvest when you notice the first amber trichomes on the buds.
But the weed is the strongest when 80% is milky white. By this time 10% will be clear and 10% amber.
Happy Harvest Buddy! 💚