Yes, you can. I get my fermenter down into the 30's when I cold crash, and I also use a cooler and water bottles. I just put like 8 bottles at a time in there to bring the temp down and swap them out more often until I get there. Once in the 30's I can maintain that temp using 2-4 bottles depending upon ambient temperatures.
I couldn't imagine trying to maintain those temps long enough to lager, though. A few days is one thing, but several weeks sounds like a pain in the butt.