If TCP/IP is working, then the problem of what file transfer programs to use, reduced to one: FTP. There are lots of user friendly, mouse aware FTP client programs available for Windows, Mac and Unix. This would make any updating of files on the system very easy for even notice users. The most common reason to transfer files is to read email offline, but this facility is provided by the email clients.
Note, use of the FTP clients does not mean unrestricted access to do file transfers: use of unrouted private networks means that IP packets can only travel between the user's machine, the terminal server, and NCF machines.