Similar to what Brian mentions, on occasion I take an older bronze bore brush and wrap a patch around it then run it through my sizers with a touch of Hoppe's on it to clean out the residual brass. I just chuck them up in my cordless screwdriver and give it a few spins then swap out the wet patch for a dry one.
After I'm done I swab them down with a q-tip and some Imperial sizing wax and they are ready for the next time I need them.
Just be sure when you clean it out really good to use some case lube and slather the insides down again. If not the first case you run in there might stick. Not sayin it is a guaranteed, but I have had it happen even with a well lubed case.
Mike / TX