I found this years ago. Its worked brilliantly for me:
Spaniel Ear Cleaner Recipe
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Ingredients:
· White vinegar
· Powdered boric acid
· Isopropyl alcohol (rubbing alcohol)
· Betadine antiseptic (or the generic version, known as Povidone-Iodine Solution)
Please note: do not use "Betadine Scrub", use "Betadine Solution"
Directions for mixing the solution together:
1. Pour 6 ounces of isopropyl alcohol in to a plastic applicator bottle. Add 1/2 tablespoon of boric acid powder. Be careful not to get any boric acid on your skin or clothes.