Looking this over, I think there has been a lot of misunderstanding by all concerned, including me, so I'll try to take the time to restate what I think is true and why:
1) Leminski has a poor shooting percentage because his Inside Shot rating is Atrocious. Since he can't avoid taking inside shots during the game, he won't improve his overall shooting percentage until he increases his IS rating.
2) you can train IS directly or indirectly by one of the combination methods suggested by darykjozef.
3) The problem with the combo training is:
a) the weekly increase is very small
b) the complimentary training bonus does not apply to this player in this situation.
4) Complimentary training does not apply because IS is complementary to Rebounding, Shot Blocking and Inside Defense. Leminski is Atrocious in Shot Blocking, mediocre in rebounding and average for Inside Defense. So he's not a 'more skilled player" in the needed skill areas. Therefore, he won't get a complimentary skill training bonus. His being good in guard skills doesn't help at all for learning the inside skill set.
So Leminski needs to have direct Inside shot training in order to achieve anything other than an insignificant improvement in his skill level.
Overall, Leminski is poorest in 'big man skills' so it will take longer for him to improve those skills than his SG/SF skills.
Hope that clarifies what I've been trying to say.