I've been playing assassins creed black flg lately and i'm trying to upgrade the Jackdaw a lot but i'm struggling to do it because i can't really find any wood or metal. They're used for most of the jackdaws upgrades so i can't really upgrade anything.

I'm looking for fast and easy ways of getting wood and metal. The fastest and easiest method to me would be looting warehouses but please tell me what u guys think is the fastest and easiest way.