When you say fermented out, how long has it been fermenting for? It isn't wise to crash it as soon as primary fermentation is complete, you want to give the yeast time to clear up any odd flavours. I would wait 12-14 days before I considered cold crashing.
I crash for 2-3 days but you could get away with bit less. I bring the temperature down by cooling the fridge ambient temperature to 4ðC and letting the beer drift down to this temperature, rather than measuring the temperature of the beer and letting the fridge go full guns until it has reached that temperature. Regardless of how you get there, it is going to take quite a few hours to get down to your target temperature. I then plan on keeping it at that temperature for at least 24 hours to crash the yeast out of suspension.
I normally bottle when it is cold rather than bringing the beer back up to room temperature.