When I paint with watercolors I like to make sure I have a nice paper made with cotton so the colors don't run.
Is the paper important for the watercolors not to run?
Yes, it is very important. Have you ever tried to paint with watercolors and had the paint just sit on top of the paper and run? You don't want that to happen.
I've never painted with watercolors. Is it difficult to learn painting?
Anyone can do it, but some of the greats, such as Alfredo Guati Rojo, really made it an art form. 
Did he have any famous paintings I might have heard of?
Probably not, but you can see many of his paintings at the museum dedicated to his work in the Coyoacan borough in Mexico City.
Did he only paint in watercolors?
That was his great love. The museum is so interesting. It is located in a house in a borough of Mexico City that remained completely independent from the city into the 19th century.