Add Record - Portal or Script?

[dxl]

I have a many-to-many relationship between Contacts and Companies. I want to add a new Contact from a Company Layout.

Do I...

1. Use a script to set the ID field relationships?

2. Use a Portal from the CompanyContact Join table?

Using the Contact Portal in the Company table does not seem to work in this case.

I know 1. & 2. work, but what would a pro do?