Hardgainer as well, and I haven't really bean able to gain decent muscle and lose fat, besides best case it's a slow narrow line you have to walk.
If you're trying to get big, you have to eat big, like humongous. I've had good results keeping overall carbs proportionately low, like 15-25% of calories.
Bulk of the calories coming from protein and fat (lots O' fat). Generally mostly primal food sources as well.