To build your superstar's overall rating quickly, go to your schedule and simulate or play to a day where you have a game to play. Do not play the game immediately. Instead, go to the Performance Institute and do what is needed to get some points. Add them to your player and leave. If you have auto-save enabled, the game will save your stats for you. If you do not, then save it. Once you are done at the Performance Institute, look at your schedule, then leave. Go back to the Performance Institute to do the drills again with your previous points still there. You can keep training as long as you do it on a day that you have a game to play.