This thread is just going to garner
more conflicting opinions...maybe the same ones you've already read.
My opinion matches
@Ridgerunner's (except for that disgusting sammich-haha!)
Let them dust where they will, if they have access to the ground that's not clay or rock they will likely make their own dust bath.
Buy some permethrin dust and/or spray to keep on hand in case you find pests when you regularly inspect them for external parasites.
My Bug Check notes:
Check them over regularly and real well for mites and/or lice.
Google images of lice/mites and their eggs before the inspection so you'll know what you're looking for.
Part the feathers right down to the skin around vent, head/neck and under wings.
Best done well after dark with a strong flashlight/headlight, easier to 'catch' bird and also to check for the mites that live in structure and only come out at night to feed off roosting birds.
Wipe a white paper towel along the underside of roost to look for red smears(smashed well fed mites).
Good post about mite ID by Lady McCamley:
https://www.backyardchickens.com/threads/my-chicken-has-mites-now-what.1273674/page-2#post-20483008