Zintro should post to appropriate industry association job boards. E.G.: post inquiries RE: WOOD MFG here: http://bit.ly/CareersInWood
Obtain permission to post . . . perform a first filter on postings (what goes where) and let the association webmaster also filter (to ensure relevance) . . . remove posts when filled . . . keep stats and only support job boards that produce results. This would, 1. - snag many part/full-time consultants and out-of-work experts, 2. - generate awareness of Zintro in that industry.