personally dont have a 'completely' homemade recipe, but it works great & can be made in bulk. Use the concentrate repel-X & mix it to specifications. It is 8oz to 1/2 gallon. Then you add 1 bottle of skin-so-soft & 1 bottle of witch hazel. It makes a large amount without breaking the bank & it works! I have 6 horses to coat in it & it hasnt let me down.

PS - I use it as a wipe, not spray, it lasts longer 

I found a recipe for it:
1/2 cup dawn dish soap
1/2 cup vineger
1/2 cup water

We found this one in the book "Complete Holistic Care and Healing for Horses" by Mary Brennan, DVM, from Trafalgar Square Publishing. In a standard one quart or one litre spray bottle, mix the following ingredients:
2 cups Avon Skin-So-Soft
2 cups water
½ cup cider vinegar
¼ teaspoon oil of citronella* (*you can eliminate this or reduce the amount if it seems too strong)
Shake before every use 


This is what I mix up to use. Two cups of distilled water, 1/2 cup of apple cider vinegar, 1/4 teaspoon of Eucalyptus oil. Mix that up, and put in a spray bottle. I have used this successfully


This works like a gem:
1 cup skin so soft
2 cups white vinegar
2 cups water
1 teaspoon ecalyptus or citronella oil
Mix it in a spray bottle and use. He also smells better than the other store bought sprays.