One tablet app, one flow with two users (specialist and customer) – how to differentiate?

I am working on a project that involves creating User Interface of a tablet app. The app will be used in the following way:

  1. a customer is coming to the shop
  2. a specialist is starting the app and initiates the flow
  3. a specialist gives the tablet to the customer and the customer is continuing the same flow
  4. after a customer is done with his part of the flow the tablet is given back to the specialist who continues the flow

The question is: do you have any suggestions how should the UI be differentiated so that it is clear which part of the flow is dedicated for the specialist and which is deicated for the customer? Do you have any good examples of similar flows?