John, you are lookng at the Personal Trainer.

You can go train your guys hard, refresh them with green packs (and fix them when needed with reds) and keep training them again and again as often as the Training is available. People on here refer to that as "Power Training". It is generally done on faster training youngsters.

This is my preferred method, I never buy Scouts or Personal Train. It takes a lot of green Boosters though!