I applied online. The process took 2 months. I interviewed at OSHA (San Diego, CA) in Jun 2018
Interview
I applied online at USAjobs, was referred to the hiring official, received an email to schedule the interview, interview was via webcam due to me being on the East coast, a few days after the interview, I had to provide a writing sample
The phone interview included a panel of professionals. It was very enlightening, and very interesting even if one didn't get the offer. They did want to know about experience, and asked questions accordingly.
I applied through other source. I interviewed at OSHA (Boston, MA) in Feb 2012
Interview
Very mater of fact. Some technical questions, some public contact questions on how one would handle certain situations and how you would help a company to comply with Federal regulations