pug has yeast infection, what works best?

Hi, my pug has what I think is a yeast infection. His armpits, as well as his ears, are turning black. We live in the south so I understand humidity can be a factor. We are going to pick up some sort of shampoo and have been using a burt's bees ear wash. Will bathing him more often help? and also how often should I be bathing him?