I dry hopped with just loose pellets like both of you, and cold crashed the carboy as well. I still got lots of hop flakes even a couple of weeks in the keg. I bottled it off the keg and just tried one last night after sitting in the fridge for a week, and it STILL had flakes in it. The beer itself is crystal clear, it just has flakes. The next time I make this, I will definitely find a way to contain the hops in the carboy. As for filtering, I have no experience, but I just kegged another IPA a few nights ago and used Gelatine, and am very happy with the results and will be using that method from now on.