I just thought I'd follow up on this... I decided I didn't like the
Behr's color, and was concerned about the white marks, so I went with
American Traditions (Lowes) instead. While both paints are the flattest
finish available, the American Traditions paint is slightly glossier
than the Behr. And I don't have the white mark problem with the
American Traditions. So, I don't know if it's a Behr problem, or if
it's a finish problem, but I wanted to post my resolution just in case
someone is searching on this topic.