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. Forexample, 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.