I applied directly to the PI. Initial communication was through email, followed that by a phone interview. The phone interview was confined to science; mostly my research, what interests me about the lab, etc. I was then invited to visit the lab, interact with other members of the lab, meet faculty members with whom we collaborate and then a presentation. I was offered the job within 48 hours. The whole process from the initial contact to the offer stage took only 2 weeks.