There are no hard and fast rules. But some things just end up being easier.
Flushing depends in your preferences and your growing method. Most people flush for 1 week. A week before you crop, give the plant only water. No nutrients. Some people like to take an extra week to ween the plant down from full nutrients to zero, as I do. But honestly I dont think it makes much of a difference.
Some people stop watering it a day or 2 before cropping. This may reduce your drying time by a bit. I've never done it this way, so I dont know if it works.
Some people think it makes a difference what time you crop (day or night). I dont thinking matters personally.
It's not that imparitive that you follow any one set of instructions. It's more important that you crop at the right time, keep the flowers in a low humidity environment, keep air flowing around them and keep the lights off.
Try not to let them dry out too fast, and dont let the humidity get too high and you should be good.