My suggestion would be to use BPMN.  While BPMN does introduce some new symbols (as compared to a traditional flow-chart) it is by far the best tool for the job.  I have used BPMN to document business processes and presented the process flows to the business stakeholders.  They had not issues understanding the diagrams.

If your stakeholders are new to process modeling then create a quick cheat sheet for them to remind them of what that various BPMN symbols mean.

Hope this helps!

- Adrian

Here it is:

A.1 An easy and often used method of showing user roles in a BPMN diagram is by using swimlanes.  Take a look how Frank used swimlanes in his process flow using the BPMN notation, in this forum thread:

http://www.modernanalyst.com/Community/Forums/tabid/76/forumid/16/threadid/363/scope/posts/Default.aspx

A.2 What do you mean by "Specific For", can you give a bit more details?

A.3 One way I have showed pre- & post-conditions in a process flow/BPMN diagram is by using a callout (text annotation) on the Start symbol (for pre-conditions) and End symbol (for post-conditions).  The text annotation symbol is natively supported by BPMN.   BPMN also supports conditions for transitions between process steps which you can use to depict pre-conditions which must be true in order to start the next step.

B I'm not exactly sure what you mean by "loan application form"... is this supposed to be a step/task in a process, a sub-process, an input to the process, etc.?  The features available vary from tool to tool but many of them support reusability of tasks and sub-processes so that you can find out all the processes which contain a given task or sub-process.  Also BPMN supports the concept of a Data Object (which the loan application form sounds like) and many tools have support for the ability to show you all the places where a given data object is being created or consumed by a step in the process.

- Adrian