Jubblies are not particularly hard to hunt. They do not actually attack you and only run a few squares away when they get too close to you. A good spot to hunt them is just to the east of the Gnome Air Glider, south east of the Castle Wars arena, in the Feldip hills. Once they are killed, they must be plucked to receive the drops. The feathers go into your inventory automatically, while the other drops appear on the ground.