I have 2 male and 2 female breeders, you could probably get away with one male but I just wanted to make sure that if one wasn't doing the job that I had a back up. I don't really think it matters what kind. I got my rats from petsmart and they have been great breeders and pretty good pets as well. I put the rats to sleep in a 32qt steralite tub. I take a small 5qt tub and drilled holes in the top, get some dry ice from the grocery store, put a few small pieces in the 5qt tub with some water and put it in the 32qt with the rats. Wait about 5 minutes and they are gone. throw them in a freezer bag and you are good to go.
One of my females usually has 13-15 babies and the other 11-13 babies. I keep all the babies alive until they are too big for me to feel comfortable feeding them live then whatever is left I freeze. I usually have 2-3 out of each litter that I put to sleep.
Edit: I also buy about 200 f/t rats every 6 months online and have always been satisfied with my purchases. Been doing this for about a year and a half now.