Hi,
You don´t have to do exactly as I did.
This is done in solid geometry.
Press Alt+LMB on a surface to select it, then use use the "copy" command (Ctrl+C)+Paste (Ctrl+V). Before closing the "paste" dialog box hold down Control Key to select more surfaces.
As alternative you can use "Solid Surfaces" with the RMB, but this will select all surfaces that belong to the solid and you may not desire this.
Jose