The best thing that worked for us was using nothing. We blow-dried my daughter's ear after showers/baths and if needed, put a couple of drops of alcohol in her ear (to help any trapped water evaporate) but nothing else. We did start using ear plugs all the time, but made sure her ear stayed dry.
It took a few days and then it went away on it's own. If it's really bad (discharge or gets worse), I would totally use olive oil and garlic (you slowly cook sliced garlic in olive oil, strain, and then use a dropper to put a few drops of the oil in the ear). We didn't use it on my daughter (no need to) but I have used that myself for an ear infection. Worked very well for me.