I would use polyquat 1 or 2 days before because you chlorine will drop, so you need to give yourself time for that to happen and then bring chlorine back up to shock levels, which with a CYA of 100 is going to be around 25 ppm. For your pool, that would be around 2 bottles of 8.25% bleach to raise from 0 to 24 ppm (doing math in my head, correct me if I'm wrong).