Does this sound correct?
I dilute it 1.28 ounces per gallon of water for spraying the birds down.
If you have an active infestation you can dilute the Permethrin 10% to 3.2 ounces per gallon for normal infestations or 6.4 ounces per gallon for servere infestations, but this must NOT be used on the birds only inside the coop, on roosts/walls/etc. Close doors and windows before spraying and keep door closed for 10-15 minutes after you spray. I would suggest wearing a face mask everytime you spray.
The residue will last up to 30 days.