I think this depends very much on how tame your chickens are generally. Mine are quite skittish, so if I want to be able to dust them effectively I need to get them tipped onto their backs.
Normally Hubby and I do this sort of job together. He will catch the girls whilst they are still contained within their coop, then bring them outside one at a time. Hubby sits on a milk crate and holds the bird's legs together in one hand, and I hold their wings to their sides so they can't flap about and hurt themselves.
At that point they really can't move. We turn then over onto their backs and nestle them down on hubby's lap so they are comfy. They usually don't struggle after that, so I dust them, check their feet, and do a bit of an all over checkup on them while they are in that position. It's handy because I can pay particular attention to dusting under wings and around the vent area when they are on their backs.
When we are done, we tip them right way up, pop them on the ground, and they wander off as if nothing happened! To be honest, sometimes I think the whole thing is more stressful for the us than for the bids!
- Krista