Greetings John:
Thanks for reaching out to UI Extension Forestry. I've written and spoken extensively about the perils of selling timber "on shares," especially quality timber like black walnut and white oak.
The best method to sell hardwood timber here in the Midwest is to secure the services of a professional consulting forester to assist you with "marketing" your timber to multiple prospective timber buyers via the "lump sum, sealed bid" format in order to maximize YOUR financial returns rather than the timber buyer.
Feel free to contact me directly at jhayek@illinois(dot)edu to learn more about the nuances, perils, and tax considerations when selling standing timber.