I’ve also heard of people in this situation having a good deal of success with a loose bulk believe it or not. They basically crammed as much in as they could justify, and then slammed the weights hard at the gym. Some insane workouts and massive craps, and 6 months later they had put on like 35 pounds, but their body fat had only gone up 2-3%. One of the dudes still had a pretty good 6 pack going.
As far as I know, they were natural.