Maggots can usually be flushed out with a strong spray of water. If need be use a little soap/water or soak the bird depending on where the wound and maggots are located.
Triple antibiotic ointment is good to use for wounds.
That's likely something you would have to research on your own.
Bad infestations, you would want to remove the maggots even if the medication worked. All of the wounds cleaned out well and first aid measures taken to hopefully prevent infection and promote healing.