A
partner portal allows partner users to log in to Salesforce througha separate website than your non-partner users. Partner users canonly see the data that you have made available to them. Furthermore, partner users can only manipulate data if you give them the appropriate user permissions.

A). Create criteria-based opportunity sharing rules for each product line. This allows you to specify criteria for sharing an Opportunity with a specific user or group of users. For example, you could create a rule that shares an Opportunity with the product engineer when the Opportunity has a certain product line assigned to it.
B). Enable Default Opportunity Teams for the Opportunity. This allows you to set a default Opportunity Team for an Opportunity, which will automatically assign the product engineer to the Opportunity when it is created. This is useful when you need to assign a specific user to multiple Opportunities.