Professional Services have been using content marketing from the very beginning. Long before the Internet and before the term was coined, lawyers & accountants would hold public lectures on new trends to raise their profile and drum up business. Indeed in the US it was illegal for them to advertise directly until 1977 so there were few other routes to market.
The idea therefore that Professional Services need a lesson in Content Marketing always seems a bit rich. But there has been a problem when there has been a digital step to the process; the legal industry has been generally slower in that regard.
Content Marketing can seem like a mysterious dark art to those who have not used it before but one of the most confusing things about Content Marketing is more its simplicity than its complexity.
Identify the core group that you wish to influence, find out what you know that can help them - and talk about that topic in a consistent way. As the article below suggests, this does need focus & leadership. However, I would not agree that you need 'digital champions'. You will certainly have people in your firm who are more and less keen to engage with any initiative but they definitely do not need to be 'digital' people.
The fact that the content is delivered on a blog post, podcast or video rather than on a stage with a lectern really is not the interesting bit. The key question is "who can most clearly address those key questions that our audience wants answering?" Digitally or otherwise.