Hi David,

In my opinion the best way to do this is to first make sure your team gets the daily 10% teamplay bonus with the help of the bonus, which improves your training skill level, after that train the players you want to become better individually.
The fastest way to get stars is to train drills with a low average skill %. You can make use of the various training tools here on the forum.
My tool you can find here: power training tool