Here the requirement is to create a prototype to show the flow of sequence. So among the tools which the designer chooses, I prefer “Axure” or “Balasmiq Mockups”.
Any tool should be carefully chosen considering the following aspect like ease of use, comfort while we are working on it, developer-friendliness, collaboration, cost, etc.
Axure provides complete set of drawing tools and has large user community.
Balasmiq Mockups is one of the fastest prototyping tools. This would be more familiar for the people who are already familiar with the Photoshop.