I have a Yooper Lagerator (pictures in my gallery). It's just an Ice Cube cooler, and I made a new lid out of foam insulation so that the airlock pokes out. By putting a water bath in the cooler, and the fermenter in the water bath, I drop a frozen water bottle in there whenever needed or just change them out every other day. I float a floating thermometer in the water batch to check on it, and I can easily maintain 50 degree fermentation temperatures. After that, I can easily take it out, do the diacetyl rest, then rack the beer and start lagering. By adding more frozen water bottles, I can keep it at 34 degrees for weeks. It's easier to do this in the winter in my basement, though! I wouldn't try it in a hot attic in the summer.
What's great about that setup is I can also bring fermentation temperatures UP with a cheap aquarium heater if I need to.