Service in such action shall be as provided in section 6653. Notice given under this section shall be constructive service on all the defendants. If, after notice has been given or served as ordered by the court and the time limited in such notice for the appearance of the defendants has expired, the court finds that there are or may be defendants who have not been actually served with process and who have not appeared in the action, it may of its own motion, or on the representation of any party, appoint an agent, guardian ad litem or next friend for any such defendant, and if any such defendants have or may have conflicting interests, it may appoint different agents, guardians ad litem or next friends to represent them. The cost of appearance of any such agent, guardian ad litem or next friend, including the compensation of his counsel, shall be determined by the court and paid by the plaintiff, against whom execution may issue therefor in the name of the agent, guardian ad litem or next friend.