Advice on making relationships

I'm currently designing a rather complex FileMaker solution and would like to get some opinions/advice regarding how to best handle the creation of related records. Here are some of my thoughts:

I do not want users to enter data directly into portals. I find this very hard for most users to understand. I also don't want them to ever have to directly manipulate the match field contents.

One aspect of the solution is a contact management system. One database contains the company/organization information. Another contains the contact information. Contacts can be children of companies, but do not have to be. I'd like for the user to enter contact info, then link the contact, if desired, to a company.

One idea I had was to create another database that will simply function as a linking tool. The user clicks the button that links the contact to a company and is presented with a little search screen in the linking database. He/she enters a few characts of the company's name and a portal displays all matches. The user then selects a company and clicks the link button...and the relationship is made. What are your thoughts on such a process? Why would it be desirable? Not desirable?

In the above scenario, how should I pass the linking values between the databases? Global field? Clipboard? A plugin that lets me create system-wide variables?

I'm really interested in hearing how other developers have handled this situation...what works...what doesn't...and what you learned in the process. As I'm at the very beginning of this project, I'd like to start off on the right foot, so any/all advice would be much appreciated!

-Rob