If by flushing you mean removing nitrogen from the diet..yes, it’s good to begin this process a few weeks before harvest. Well, flushing will not ripen the fruits, but time will.
I have seen people remove the tops and leave the bottoms to mature further. I’ve seen bottoms harvested early and just get tossed into the trim pile for hash/butter making. I tend to let the tops go until the bottoms are all caught up. I do not continue nitrogen during this process.
Hope that helps.