Can see the setup that drives the tūī on Tiritiri Matangi mad in this video at around 0:52. Similar to an american hummingbird feeder but with much larger holes, and often oranges and other fruits like pears and kiwifruit on the nails around it.
https://www.youtube.com/watch?v=SaeObzcqCDk
Since they drive off all the korimako and other small birds, a bowl feeder (similar to this but with a large bucket rather than wine bottle https://www.inaturalist.org/observations/55367652) is set up in a cage with a smaller entrance for the hihi and korimako. Both types get absolutely mobbed the second they’re refilled in the morning (but obviously in a place with much more dense bird populations), so they definitely work if the birds see them