In the past I've always dryhopped the day I kegged and it went into the cold, but I've never been happy with it. After reading some of this and thinking about it, I'm going to try transfering from the fermenter to a Co2 flooded keg, add my hops and seal it for a couple of days before carbonating it in the cold. Maybe it will be more of what I'm looking for. 
After years of trial and error, my latest way of doing this is:
- Primary until fermentation is complete, let the yeast drop
- Rack to a keg containing a sure screen. Dry hop in the keg with leaf hops loose or pellet hops in a nylon bag. Purge the headspace with CO2 and add enough head pressure to seal the keg.
- Store this keg at cellar temps for 10-14 days.
- Do a keg-to-keg transfer to my serving keg. Carbonate and serve.