Any reason why you're racking to secondary? I'd just dry hop in the primary unless you're planning on reusing the yeast. If you're absolutely set on a timetable, you can add the dry hops in the primary before the krausen falls. I've done this and the beer has been fine. I wouldn't rack to secondary if the primary fermentation is still chugging along, though.
If you're not on a strict timetable, I'd just be patient and let the yeast tell you when they're done.