How to copy contributors from one project to another in TFS2012?

Hi, hopefully this is an easy one.

I've just setup a new project and I need to copy contributors from an old project to this new one. Under TFS2010, I used a power tool extension that provided me with a "Team Members" group in TeamExplorer under which I dragged  contributors from one project to another. How do I do the same job in TFS2012? what I don't want to do is select 100 checkboxes, I'm happy to go to powershell if that's all that's available.

Thanks