Ask how a practice tests a message with real audiences and how it hands the result to you. A good fit leaves you with language you can use without them.
The directory has two vetted practices that list messaging among their specializations: Mashman Consulting Group and JaKe X. They are based in Barcelona, Cataluña and Little Rock, AR, and they are one consultancy and one independent consultant.
As for how they work, one offers done-for-you work, where the practice does the work; both offer done-with-you work, where the client works alongside the practice. Of these, one works with clients remotely anywhere and one works both remotely and in person. Their working hours follow Central Europe and US Central time. On the PBA scale they span price tiers $$ to $$$$ (what the tiers mean). Every practice here passed the same seven-criterion review, whatever its specialty, and the sample listings never appear on this page.