Tracking powder works well but is strong and needs someone who is licensed to put it out. When we had it used it was put in the holes around a building not in outside runways. 
They get it on their feet and then lick it off. You don’t want dogs or cats to get to it. 
We haven’t seen any rats for a few years but we have a pest control service come monthly. It is some of the best money spent. 

Chuck