I think there not much can be done to improve scoring from FK. Certain skills might improve it a bit, but if your player already at good Q and almost never scores, then he has not the needed hidden talent for it. You should search for other options then.
My current FK taker begun to score often from 18yo without any training. In my 2nd test team I bought a striker without any SA and tested him for freekicks, he scored more often than players I have had even with better shooting skills. So I gave him SA which (I think) made his freekicks one step better