Before promulgation of any regulations establishing a compact over-order price or commission marketing order, including any provision with respect to milk supply under subsection 9(f), or amendment thereof, as provided in Article IV, the commission shall conduct an informal rulemaking proceeding to provide interested persons with an opportunity to present data and views. Such rulemaking proceeding shall be governed by Section four of the Federal Administrative Procedure Act, as amended (5 U.S.C. Section 553). In addition, the commission shall, to the extent practicable, publish notice of rulemaking proceedings in the official register of each participating state. Before the initial adoption of regulations establishing a compact over-order price or a commission marketing order and thereafter before any amendment with regard to prices or assessments, the commission shall hold a public hearing. The commission may commence a rulemaking proceeding on its own initiative or may in its sole discretion act upon the petition of any person including individual milk producers, any organization of milk producers or handlers, general farm organizations, consumer or public interest groups, and local, state or federal officials.