I want to try to do a concrete-like finish for a fireplace wall (it's just flat dry wall now). Is this method you mention above the only way to achieve that look?

No, there are plenty of concrete-like finishes you could use. If I were doing this for a client, I'd use Swedish Putty or Stucco Veneziano or a concrete microtopping. For the latter, check out getrealsurfaces.com.

Would venetian plaster achieve this look? I thought it is very flat and shiny.

Thank you. I know a person who does Venetian plaster but he seems to be reluctant to make it look like concrete. He says it doesn't turn our great. Any chance you know a person in the SF Bay Area who can help me render this look? It's a small project in a loft-like condo.