Hi J. -
I didn't have ear infections as a child, but I did have problems with wax in my ears, so I used to have them irrigated at the doctor's office. He'd fill an ear with a warm solution, let it sit there for a minute, then let it drain out. You might want to ask your son's doctor about irrigation. Don't try to do it yourself, though, as if you use plain water and don't get it out completely, you may leave bacteria in your son's ear which could cause further problems.
PLEASE do NOT insert a syringe into your son's ear, as someone here mentioned. This is potentially dangerous, as the pressure of the suction on the eardrum can damage it. Also, ear "candling" is a questionable practice for anyone, but DEFINITELY should NOT be done on a small child...
I don't know much about garlic oil, but that sounds fairly innocuous to me so if others say it works, I'd give that a try. Just be careful with your son's little ears - wax buildup is better than the injury you may accidentally inflict trying to get it out.
Good luck!