Adam, is this an attic dwelling rat? I've had a few smart ones that I had to take extra measures to fool, and others that just needed to be starved out. I used clean, unbaited traps (woodstream's pro model with the big yellow trigger)and covered them with insulation, set right in their trails, like a blind trail set for fox or coyotes. With cellulose it's easy to completely hide the trap. I even remade the depression from the trail right over the trigger. Loosefill fiberglass is a bit tougher, but you can still blend it in. Just don't overdo it or you'll have too much insulation between the kill bar and board when it slams shut. You're using gloves while setting traps, right?
Most of our rat trapping is done after the building is completely sealed and interior food sources secured, so we've cut them off from their food supply inside and out, making it easier to get them to a baited trap. If they're smart to one style of trap then change to a different style and change up your bait at the same time so they don't associate the new trap with the old trap.
We had a commercial job that required 3 days of external sealing and 5 days for interior restoration. We removed/replaced every ceiling tile and all insulation in 9000+sqft office building because everything was covered with rat feces and urine. We had the client remove all food sources and move the company's operation to a different building. The rats, over 100 of them, hadn't had a good meal in 3 or 4 days when we started setting traps. We would watch them run to baited traps to get food, three times catching two at a time. We removed 99% of the rats during the restoration phase. However, I had one old male that somehow managed to stick around for about two weeks without getting caught, He finally succumbed to Kirk's Dark Magic and WCS's Squirrel NB. On a promotional note, WCS now sells the Squirrel NB in a caulk tube type dispenser. You can bait a dozen traps in about 12 seconds. Quick and mess free baiting.
