On withdrawal time, everyone should do their own research and make their own choices. Some feel chemicals like Sevin should not be used around chickens at all. That Ohio University vet school paper I linked above talks about using it on both the birds and on coop surfaces and in nest boxes. I often see DE recommended as an alternative, but I've also read of experiences with it showing it is only minimally effective, if at all. You should of course avoid inhaling either one.
