Hello @anon25517230, welcome to the Asana Community Forum 
The main task is it always assigned to the same person or reassigned as it moves along the stages? If so then automating it with rules would work.
Maybe this helps: Approval Workflow - #2 by Andrea_Mayer
Rules for subtasks would be possible with Flowsana
And here is the relevant feedback request thread for rules on subtasks: Allow Rules for Subtasks