For wild lowbush blueberries where the plants are like a carpet, a wide rake works quite well. A wide rake is too cumbersome for highbush berries.
For cultivated highbush blueberries a narrow rake works best. I prefer a rake that's only 4.5 inches wide.
Yes, You'll get a lot of leaves, stems and such mixed in with the berries, but the increase in speed of harvest far outweighs any time spent cleaning the berries which is easily done on a table or the like.
FWIW, A wide rake also works phenomenally well for harvesting dandelion blossoms for dandelion wine.