Smart lists... Member of list "that list name" AND Age is over 30, AND State is: TX, CA... Something like that.
Unless i'm misunderstanding what you're asking?
Have you considered utilizing Lead Segmentation? Here are the walktrhough for doing it.
Are you just trying to split the list into smaller lists of roughly the same size?If so, create a smart campaign with the filter "Member of List", referencing the master list, and then use the Add to List flow step, with choices using random sample to split them into smaller lists.
The process is outlined here:
Retrieving data ...