Are the bugs long or like dots? If they're dots, they're mites. (You can only see them at night on the birds, and then rarely). IF they're long, they're lice. (They stay on the bird.)
If lice, you can fill a knee-high panty-hose with the permethrin and use that to dust them. Or use the shaker can. I find it easier to shake a little onto my (gloved) hand and apply that to the bird - under the wing, at the vent, on the chest, back of neck, etc. Ruffle the feathers to get it all in their feathers and against their skin. In fact I had to do it today as a follow-up to last month's lice treatment. (thanks to either a goat or some vulture).
Also dust under the bedding (scrape aside, dust, return bedding) and in the bedding (dust bedding, stir in) and nest boxes.
On the mites, you can get "goat lice spray" (also permethrin) and spray the wood of the walls, the nest boxes, the eyes and joints in the coop. mites stay off of the birds so you must treat those areas.
Redo everything in 7 days twice.
Personally I do not recommend Sevin as it's carbryl and we're learning more about how it's a bad chemical to deal with. I believe it's even being taken off of the market completely this year.
Incidentally on the worming, worm FIRST with wazine (piperazine). then in 2-4 weeks worm with a broad spectrum full wormer like fenbendazole (wormazole, safeguard etc) or pour-on ivermectin. If you follow up with the pour-on ivermectin (5% ivermectin cattle wormer blue liquid) that will also kill the hatched external mites/lice. You still have to treat the premises though always.