Reader's Digest used several artists for portrait assignments but my favourite of that group is Karl Godwin.
I think that's because Godwin's style has just a touch caricature in it - a subtle cartooniness that lends a little more character and humanity to his subjects.
Karl Godwin was born in Canada but got his art education in the States - at the Art Students League. In 1922 and '23 he taught commercial art courses at Chouinard Art School in Los Angeles. By 1940, he had returned to New York City and eventually moved to Westport, Connecticut where he lived until his death in 1962.
You'll find some example's of Godwin's painting style here.