The basic snap traps will work. It will take a couple of weeks to get them all but will do the job. The best configuration I have found is to have two snap traps with the long base sides parallel, a few inches apart. Elevate the opposing sides so that the two traps are now in a shallow "V". When Mr Rat is able to jump back away from the closing bail on one trap, he encounters the other trap, leading to a speedy demise.
My wife and I rented a deserted farm house years ago. It was vacant except for a population of rats. The snap traps got them all. My best catch night was 19 rodents eliminated. "SNAP", there's another one gone!