I'll add that he also was very, very good.
This post features some of his covers for the weekly magazine Para Todos, which another brief reference holds that he owned and edited for much of its 1920s existence. The title's literal translation is "For All" though perhaps a better, looser version would be "Everybody's" -- also the name of an American magazine published 1899-1929.
All the Para Todos covers I found on the Internet were done by Carlos. But given their quality and on occasion elaborate nature, I almost can't believe that he was able to create a cover every week in addition to his other activities.
Here is a sampling: