The summons must be accompanied by an affidavit of the plaintiff or the plaintiff's agent, representative, or attorney that the judgment or some part of the judgment remains unsatisfied and must specify the amount due. It is not necessary to file a new complaint.
Affidavit To Accompany Summons -- New Complaint Unnecessary
Mont. Code Ann. § 25-15-103, under Applying Judgment to Joint Debtor.
Mont. Code Ann. § 25-15-103