Drury’s (1984) Assertive supervision: Building involved teamwork helped me figure out something really important.  In regular assertive training, we ask the trainee to use the DESC model. 

Describe the incident, Express your feelings (so blue), State what you want and describe the Consequences.  

Drury’s model states the same DESC model but with a very important twist.  Instead of Expressing feelings, we need to Express why the person’s behaviour is a problem for me or the organization.  Most workers don’t really care about the feelings of their supervisor.  We need to use objective and unloaded language to describe the incident.  In expressing company policy, we have to confront how some behaviours create tension with other workers or with higher management.  S is for the Specifics of what I want the employee to do.  Consequences can be both positive and negative for changing their behaviour (p.184).

Let me know how this works out for you