"Flushing" is done in the last 7-10 days, usually only 5 in hydro. Lowering the nutrient strength in the root zone causes osmosis to draw excess elements from the plant, out into the nutrient solution. You can actually watch this process happen with a ppm meter over those 5 days. Cool stuff.
You want more trichomes? You really have to start with the right conditions at the beginning of flower. Trichome density is a genetic expression of the plant, triggered by environment. (look up trichome bearing plants) It's a bit late in the game to *spur* additional trichome production, you're working on filling the trichomes already produced. :)
Resin production is highest when the plant can focus all resources toward that goal. Excessive elements slow that process, improper growing conditions also slow that process. Some conditions can destroy
terpenes before harvest as well.
You know you're doing something right when your trichomes are still plump after drying...
Douglas