Regarding the blender, and mortar if you are a traditionalist, I would recommend blending without any liquid if possible. The liquid you use should be only enough to carry the food down to the blades in the blender. Any more liquid and you risk the food lifting away from the blades.

A similar problems occurs when mashing, for instance, beans in the mortar and pestle. Liquid allows the larger pieces to glide more easily out of the pestle's mashing grind.