Generally the rule is lower quality, easier training. So if its fats trainer it's gonna be easy to train him.
Yes, that's the general rule and like @Ποσιδονας wrote

A 5* 80% academy 14 token player need 35 greens to get a sa.
A 5* 95% ft, new player, need 50 greens.
it's correct but only for the newborn players (academy or from the market).
If it's about a 85-90% q player you had from previous season but has some skills very high, then you must follow the post #3 example and find the drills with low skills