Lowering an aileron gives that wing some added drag and lots more lift. Raising an aileron causes the wing to have a lot of drag (remember, the air travels faster on the upper surface - hence the ability of a model (or any aircraft) to fly
No, this is not correct. The aileron going down has a higher drag than one rising the same amount. So for differental, the ailerons move up more than go down to balance drag between the wing panels thus preventing yaw.
Secondly, if the model is going faster than landing speeds, raising both ailerons will cause the airplane to climb, so they do not alway act as spoilers, they can act as elevons as in a flying wing. Raising both or lowering both have some interesting trimming effects.