Smoothing patches from meshed surfaces for shelling complex models

Shelling complex models in rhino is a proper pain.
So Ive been looking at making a patch from a mesh copy of my surface to be offset to make my interior wall.
However this obviously generates a lot of unwanted interior detail which I want to smooth out. (I got this idea after looking at Zbrush shelling tutorials)
So what is the best way to relax my patches interior detail? If this works this will be a wonderful way of shelling models quickly with accurate boundaries so you can ensure all your multi part models fit together nicely.

I will post examples and pics if anyone is interested in this topic.

Thank You.