There was a thread not too long ago about tossing a hop pellet into a glass of BMC, or other hopless beer-water. I've tried it myself, it's not bad. If all you have is some Keystone or Natty Light, it certainly helps.
Filling a growler and dry hopping seems like a waste of hops though. A few ounces of pellet hops will go a long way compared to dry hopping a gallon at a time.
Then again, this is probably an upside of living just outside Milwaukee. While we've contributed too much to the mass market sh*t beer out there, it's also REALLY easy to get your hands on great beer here too!