Here in Alabama, all private property is considered "posted". No special markings or the presence of "Posted" or "No Tresspass" signs are required.
For hunting purposes, the hunter must have in his/her possession, written permission from the landowner that clearly defines the permission(s) granted and the time frame those permsions are valid. This document must be signed by the land owner.
I would suggest that you go a route similar to this, thereby eliminating any issues down the road.