For everyone
Training is separate Fitness center (Acceleration,Agility,Balance,Jumping,Pace,Stamina,Strength) and Training Facilities (Set Pieces,Crossing,Dribbling,Finishing,Heading,Long shots,Marking,Passing,Tackling,Technique,Aggression,Creativity,Decisions,Determination,Influence,Positioning,Off the ball,Teamwork,Handling ,Reflex,Kicking,One on ones,Rushing out,Aerial ability)
So 1. I suggest you should upgrade Training Facilities minimum level 4 cause it's cover many skills. On match date change to train fitness because it's count from match play*Progress rate.
2. If you set Specific Skill... when you play match, you will get 75% from match play. If you want more, you must set random skill (Default,Attacking,defending and etc.)
3. If you want to train mental (Aggression,Determination and Influence), you should train when your player nearly to full rate but you can't train when you max rate because you will get 0.02 or 0.03 when your rate was full. **when mental is up, the value player is no up so I think it's free point, no deduct from Limited Ability but I'm not sure and you must use long time for it**