Fly protection for dog

Hello,
It’s very hot and loads of flies and there is an abundance of other insect unpleasantness.
My friend’s dog is suffering from fly attack on the ends of her ears.
We have tried clay, wax,oils, creams, orthodox repellents; a long list of stuff.
Yes, we have tried DE concoctions and incense.

Some of it works well but only for very short periods of time, like 1/2 hour.
Friend manages her horse protection very well but the dog is a challenge.

They live outside. My friend is in the tiniest of horse drawn caravans.
Lana is long haired, pointy ears, she is a German shepherd possibly.
Any advice, experiences most welcome, particularly by Lana.

Thank you, merci, a bientot, with sweaty steaming blessings
Stay cool
M-H

Your friend could try catnip tea, placed upon the dog's ears.  I have found catnip to work wonders of most flying bugs, I would hang fresh bunches at the doors to keep the flies away.  And have used the same tea on horses faces to deter flies.

Of course if there are cats around the dog may become the cats new best friend!

Peace