We are kind of trying to do the same thing.
We are accessing MS Dynamics CRM data. Each customer is owned by a sales rep.
So our section access is based on the sales rep employee number.
So a rep can only see his/her customers where they are the owner. A manager can see a group of employee numbers and thus all of their accounts.
We are not going down to the customer level at this point. So a user will be able to see all accounts owned by the employee numbers that appear in rows in our Section Access table.
Our solution would allow the one rep in your scenario to see all of the customer/products for the other rep. which doesn't sound like what you are trying to do.