(a) The commissioner shall adopt by rule, subject to Chapter 13 of Title 50, the "Georgia Administrative Procedure Act," and maintain an appropriate procedural manual for use by county property appraisal staff in appraising tangible real and personal property for ad valorem tax purposes.

(b) The manual adopted by the commissioner pursuant to this Code section shall be utilized by county property appraisal staff in the appraisal of tangible real and personal property for ad valorem tax purposes.