I would use TTO on the bug bites (I'm repeating myself here ;)...)
My Dad (and I think Ellie Mae you do this) would take a glass mason jar and a rag or sponge, pour some of the fly spray into the jar, just enough to wet the sponge/rag. Wipe the horse down, and replace the sponge into the jar and seal the lid. Reuse. You will not need to add more bug spray everytime, just when the sponge starts to really dry out. It saves a lot.