not sure when help please

this is my first grow, I began flowering my plants today, i know that tricromes need 15% amber, 80% cloudy and 5% or so clear. I also know i need to flush them multiple times prior to harvest to get the nutes out. My question is when should i begin to flush? At what stage of tricrome development? Also what is the best way to spike the colas without damaging any root structure. I have 5 girls all Nirvana strains blsckberry, WW and Ice. Any help is greatly appreciated..

9 to 11 weeks for the BlackBerry, and 8 to 10 weeks for white widow and ice, are what Nirvana recommends for flower period.. Is this a good guide to go by?

Flush the last two weeks, which of course is a guess at the time. I wait until buds seem to slow or stop swelling.