Denali -- when I dust my birds, I hold them upside down by the feet (they don't like it at first but quickly settle down) and using a dispenser like the ones at pizza places for peppers and cheese, I cover them with Sevin Dust. I am careful not to get the dust in their eyes.
By 'hanging' them by their feet, I'm able to get the dust to their skin, under their feathers easier. If you're fully prepared ahead of time, they don't 'hang' long.
I know there are a lot of people who don't approve of this practice, but it's what I do and what works for me. Other people also use DE (diamethisomethingearth---sorry, I don't know the official name).
Also, when I clean out the hen house and next boxes, I take all bedding, waterers, feeders, etc out and using the cheese/pepper shaker full of Sevin Dust, I cover the entire area (usually including myself).