I think a regular dermatologist should be able to help you out. If not they should be able to refer you.

I never look around for English speaking doctors personally, since in my experience every doctor I have ever been to has had enough English to tell me what the problem is and how to treat it. Obviously some are better than others, but never had any problems.

I personally went twice to a guy in Kyung Sung Dae. In the building next to Perugio apartments above the Angel in Us coffee shop. Forget the name of the place, but just look for 피부 which is dermatologist.