Here is something simple you can do, which works for me.
Consider player X. You badly want o improve his technique.
- Make new schedule especially for him. Make it so at the beginning it is exactly the same as the general schedule (or youth general schedule, for youths).
- Since you want to improve his technique, increase his "ball control training" alone to the right. For some players a small increase can make a difference, for others even a big one will not. I usually start by taking it to the first notch of "high".
- Then, decrease all the rest regimes evenly, so that the total workload remains where it was.
- This is now a schedule that improves the probability that gained Ability will be on one of the Ball Control attributes, where technique belongs.
- If you really don't care about e.g. his defensive attributes, you may decrease the defensive regime a little further and use this workload to increase Ball Control training even more.
- Check regularly to see if the player has become "unhappy with high training workload". If this happens, try to lessen the regime imbalance a bit and see if he is happy again (within a week).
- Wait for a couple of seasons. If Technique improves enough and you are happy with it, take him back to general training again.
- I have used this method to increase the PACE of a youngster from 8 to 15. Of course, this happened over a lot of seasons, and he had a lot of Ability differential (PA-CA) to give. Unfortunately, nothing else improved.
- Keep in mind that if the player doesn't gain any more Ability, then if his Technique improves, something else will decline. This part is a bit complicated. Chances are that he is going to decline on something that he was already good at, because light training is enough for what he is bad at, but not enough for what he is good at. You may want to heep his physical training to where it is and only decrease the rest of the regimes, because physical attributes are the hardest to improve back.