I did a batch with 1/2 oz last year that was pretty tasty...I had success adding dry hops and rosemary in the keg, then racked to a new keg after about 4 days, rather than the week he recommended.
There was a front page article a few years ago: https://www.homebrewtalk.com/bittering-hops-in-15-minutes.html. I used the method once or twice successfully.