I bought 500 pieces 38 special brass the other day...most of it was beyond "once fired", as several pieces had evidence of having once been nickel plated. I also found some "Super Vel" and other old headstamps in the bunch.
Much of this brass that I bought had already been deprimed and resized(although I don't think tumbled). Some of it had even been expanded. I dumped the whole lot into my "38 special to be processed" box and have been working through resizing and then sonicating it. In other words, I didn't treat it any differently from my other range brass.
Any brass I get from unknown sources get this same treatment, so I'd rather not pay extra for someone else to do it too.