AW Computing uses a private sharing model for opportunities.

AW Computing wants to grant access to all users in the Service Manager role for Opportunities of type Service Agreement in a private sharing model.

Criteria-based sharing rules allow sharing records automatically based on field values (e.g., Type = Service Agreement) to roles, public groups, or users.

Salesforce documentation confirms that when the org-wide default is private, sharing rules are the declarative way to grant access to specific users based on criteria. (Salesforce Help)

Owner-based sharing rules share based on the record owner, not a field criterion.

Apex sharing rules are needed only if declarative sharing is insufficient.

Manual sharing requires user action and is not scalable.

===========