How to assign a user to administer one content type only?
The xpress is not an admin, right? So the xpress won't be able to see the admin toolbar. Have you tried accessing the link of node/add/testcontent, node/node-id/edit? was xpress able to access it? if yes then you need to provide a link/button for the xpress to see when he/she logs in. Then I think you need to use views to show the lists of TestContent where xpress can search/filter.