Training against computer


I am wondering what is a good way to train against computer opponents? Right now I use the stockfish engine on my iPhone 5. I get out a real board and make the moves on there. I am about 1400 so I set the engine to 1500 to play against. It beats me most of the time, sometimes I can draw and one time I won. Is this a good way? Or would I improve quicker if I cranked it up to 2500 and let it kick my butt.