I agree that Content Marketing should definitely be part of the mix. Content topics that offer valuable information on how to expand internationally would be key. Highlighting the biggest challenges and how to solve them.

I would use LinkedIn and Medium (and other social platforms) to push the content out but I'd utilize your website as "home base" for the content. You have more options and flexibility with efforts on acquiring opt-ins - which gives you an idea who is expanding internationally.

Publishing search engine optimized content on a blog is a good place to start. Have a place to draw people in to get a newsletter opt-in with an email address and more expansive offer downloads requiring more contact info. Plus, you can set remarketing tags so when someone does hit your site, they'll see ads from you on Facebook, LinkedIn, and other sites after they leave. Offering your content for download in those ads would be a good idea until they convert.

Are you considering Facebook/LinkedIn ads to try to hit targeted personas. I'm sure you have a good idea of what titles and functions in a company would be charged with executing international expansion. Some nicely targeted ads at those people would be good. The targeting on both platforms should help you narrow in on a good sized audience.

Google or Bing PPC might be a good option as well. A quick look shows a bunch of international business keywords that get traffic. Companies looking to start expanding internationally will for sure be searching on best practices and how-tos.

Those are just a couple thoughts. Let me know if you'd like to brainstorm further.