Forum Moderators: rogerd
I'd ask firms you speak with who will be doing the posting and get some client references. Having posts of reasonable quality is important, and that's a subjective judgment. A bunch of "me too" posts or posts that don't make sense in the context of the forum won't help much.
You might be able to solicit help from freelance sites, too. As always, look for a long and excellent history of completed projects of the scale you anticipate.