[Bronstein]

Chess: It takes years to become good. It's a whole process of maturation.
Poker: In a few months any student can get good. Just learn the math and then some.
I define good as never making a worse decision than a weak player. The weak player can be someone who studied the basics or someone with years of experience who never studied anything.

Assuming he has the skills I can make someone a good chess player after years of individual training, a good poker player within months by giving him the good books.