Don't know if it has been covered on here before, but this is the recipe my local vet gave me to use at home. I got a little squirt bottle from the store and rinse my dog's ears out everyone once in a while and do it especially after hunting in some nasty water like old stock ponds that cows frequent.
1/3 water
1/3 vinegar
1/3 rubbing alcohol

As explained to me by the vet; the vinegar creates an acidic environment that cleans and keeps bacteria and what not from growing. The alcohol kills the bad stuff and helps dry excess moisture out and the water is just a buffer that dilutes it all down. Put a small squirt down their ear canal and rub around for few seconds. I've never had a dog get an ear infection or have sore ears. Just thought I would share.

I got a recipe a lot like this but it calls for a few other things... works like a charm... we had a dog that needed drops every time she hunted in water... was a pain but she was a good pup...

Thanks for the tip.. I will have to try that.. We have been getting a foaming solution from our vet that works great but this stuff is by far cheaper I bet

Whenever any of my four of my dogs come up with that "brown
gunky" ear look, this is what I use. It's simply called "Purple Solution.

I will use it more for maintenance when doing a lot of water work.

If they start shaking their heads for no apparant reason (without any
sign of the brown yeast infection, I take them to the vet's immediately.
It's not unsual to get a weed seed or stem jammed into the eardrum.
Once it passes all the way through, it becomes life threatening. Plus, in
that situation using "rinses" is not a good idea.

16 oz. bottle witch hazel - Walgreen's (off the shelf)
4 tablespoons Boric Acid Powder - Home Depot (off the shelf)
16 drops Gentian Violet 1% Solution - Walgreen's (ask phamacist)

For most persistent ear infections, I use Tresaderm (from my vet)

I use Tresaderm because Sadie is very prone to ear infections.

1/2 white vinegar, 1/2 rubbing alcohol is what I rinse my ears with when scuba diving in the rivers during the summer. Always had ear problems in the summer until I started using it after every dive.