I've been using this technique for a while now. When I first started, my beers were too bitter. I adjusted by adding my bittering charge at 30 minutes left in the boil but enter it in beersmith as a 60min addition. At flame out, i add all the rest of my hops calculated in BS as a 20min additio. I then whirlpool for 5 min with a pump, then let it sit for 20 min. I have been working on this for over a year and this me4hod nets me the best results. Tons of hop flavor with none of that sharp bitterness.
Oh yeah, I always dry hop in the keg. I have 2 kegs reserved for hoppy beers only, since the smell never goes away now, even after extended soaking in pbw.