[dazydaizee]

I personally don't pluck my poo mix's ears because there's not much in there and they're in good shape. A huge factor with ear infections is food. Usually hair is a very minute factor. As far as clients' dogs, I pluck enough to allow air flow in those that have been plucked in the past. There are a few I do not pluck and a few that have such huge amounts of hair in their ears that it matts.
I plucked a Lagotto Romagnolo's ears today. He's never in good shape and his ear hair & ear wax/gunk had matted into an oblong clump that filled the entire ear canal. Horrible. Obviously it was necessary to pluck.
Overplucking can cause ear infections (inflammation from the plucking can be a perfect opening for bacteria), but lack of air flow offers a moist, warm environment for yeast & bacteria to grow. So, in my opinion, minimal plucking is usually best. And I typically shave out what I can and a good amount of the inner flap depending on the dog (breed, history of ear infections, current ear infections) to allow for more airflow. Then I'll pluck enough to allow adequate air flow into the ear canal.

 

[dazydaizee]

If the ears are inflamed and sore I would imagine an alcohol based cleaner would burn.. But if you use a cleaner to pour into the ear canal it should have a drying agent (like alcohol) so that the ear doesn't retain excess moisture making the problem worse.
I would only pour a solution into the ear of a dog with an ear infection or a LOT of debris deep in the ear canal. The canal is L-shaped, so you're right, you can't reach all the way down with a wipe, however if the dog isn't having issues, you might cause more damage by pouring solution in. It can cause excess shaking and scratching which can lead to inflammation in the ear and allow bacteria and/or yeast to thrive.
Especially if your dog has yeast problems with the ears then it makes sense to use a solution with vinegar to change the pH of the canal creating a less ideal place for yeast & bacteria to thrive. But if your dog's ears are doing well and there's just some normal waxy discharge, an ear wipe or swab soaked in cleaner is a much better route.
If your dog does have chronic ear infections I would evaluate the food he's eating before anything else.