Sanding works best on CS with a white core, like CTMH's. Then you can ink or chalk the white space if you wish.

You can also distress the edges of your CS by running a scissor blade along it.

Apply ink directly to paper by running your pad lightly over the parts you want distressed. This looks good with any color of ink, but browns in particular.

A water and reinker mixture (experiment until you like the results) in a spray bottle and spray your CS.

Tearing also gives that aged look. For extra shabby chic, ink the edges with a similar-colored ink.