We went to see the grandparents today and grampa showed me an easy way to unclog a slow or clogged bathroom sink. Close the drain and fill the sink with hot water. Plug up the sink’s top vent, open the main drain, and use a plunger on the drain. Pulling on the plunger is what does most of the cleaning. The water in the sink keeps the nastiness from splashing out at you. I just tried this method and it works great.