selecting the surfaces for surface-to-surface radiation

Hi,

When I definie the surface-to-surface radiation boundary conditon, it is quite troublesome to select the surface one by one.

Is there any easy way to select all surfaces for surface-to-surface radiation other than selecting them one by one?

I tried Selected All, and found that some unwanted surfaces are selected, for example, the contact surfaces between two adjacent solids. Does it matter even though I have selected those unwanted surfaces?

Thanks.