First off to reply to Sherian, fungal infections by no means have to have a whitish crust. Scratches is commonly fungal and I have never seen scratches with a whiteish crust, ever.
Second, if it was a reaction to fly spray I would expect this same thing on other delicate skin areas, not just the face. Neck doesn't really have delicate skin like the belly, or between the front legs.
I would definitely be using something to treat a fungal AND bacterial infection. Yes, they make shampoos and sprays that will treat both types.
Every fly spray I have used has been oily. And citronella is a very very common ingredient and is usually needed to be effective. Ever heard of citronella candles to keep mosquitos away? And fly spray should never ever be sprayed on the face anyway.
I have no idea what hibitane soap is so I can't comment on that.