Luffy got the best training, arguably cause Ray is the most experienced out of them.
Mihawk also explained alot stuff to Zoro, he seems to recall it every time he needs to. In the recent chapter it was revealed that he has brain deficiency and litterarly forgets the most basic shit he was told for no reason, like about CoC
We got literal confirmation what sanji "training" entails and was said in the manga during the timeskip and by some people doubted (cause they cant read):
Sanji defeated 99 okamas and ran away from them, he got no lesson in Haki, fighting style, or explanation.
So in that order, i would say