Regarding flys and nats.... once you get back home grab a couple of Bug Bombs, Ortho, Raid, or whatever, The kind where you prep the house, set the things and get out quick closing and locking the door and come back hours later.
If you do not have pets you can do this now, but I prefer to do it at home.
HINT. Vets have better stuff than your local hardware or other store.
But I found the stuff I got at the super store (Meijers in this case) worked just fine.
Home is where I park it!