Cool thanks guys! I found a video on YouTube that was pretty helpful also, I think it's what was being described in the post I linked to.

http://youtu.be/Vf_PVG6VJSE

They have a rack with 4 of the the really big cement tubs. Each tub has 3 males to 12 females. The females are removed to a smaller tub in another rack to give birth and wean. Then the babies go into a big tub to get raised up to the right size.

I'm definitely going to give it a shot. I'll probably come up with my own method sense I think 15 rats per tub sounds crowded but I like rats so it will be pretty cool =P