In Kenneth Koch's Modern (1800-present) English Poetry class, the biweekly assignment was to produce a plausible imitation - but not a satire - of the poet in question.
It was a good way to try to get into the head and the rhythms and the images of a poet. Some were easy: Whitman, Eliot. Some were very difficult: Stevens, Yeats.
I see Auden imagined a world in which poets were so much in demand that they required apprentices to help out:
If poetry were in great public demand so that there were overworked professional poets, I can imagine a system under which an established poet would take on a small number of apprentices who would begin by changing his blotting paper, advance to typing his manuscripts, and end up by ghost-writing poems for him which he was too busy to start or finish. The apprentices might really learn something...
Whole piece here.