In this lesson, we find that Manual Sharing is not currently available in Lightning Experience, thanks to the Lightning Roadmap. We switch to Salesforce Classic and create a Sharing Rule on the Opportunity. 

We set the criteria for the Opportunity Sharing Rule so that whenever an opportunity has a Lead Source of Web and a Stage of Closed Won that it is shared with those in the Role of Western Sales Team.

We update the John Doe user record to reassign him to the Western Sales Team Role and then update an opportunity to match our Sharing Rule criteria.

Thanks to the magic of the Sharing button on the Opportunity page layout, we see that John Doe now has access to the opportunity that we updated to match the sharing rule criteria. We then manually share this opportunity with a couple of other users individually, via manual sharing.

Important Note:Role Hierarchy opens access vertically and Sharing Rules open access up laterally. Manual Sharing opens access flexibly.

Resource:
Lightning Experience Roadmap - https://help.salesforce.com/articleView?id=lex_roadmap.htm&type=0