I have been using the 'ear dropper' technique for years, an outback guide in Northern Australia gave me the idea while swimming fresh water lakes in Kakadu. This might be wrong, but I go ahead and us 100% alcohol (which is not 100% it turns out), I had a bad experience using some old vinegar one time, and did not look at the bottle and it gave me a 'nasty, nasty' ear infection that only anti-biotics could fix. But I use this mixture nightly after diving or after heavy swimming, sure does the trick.