In summer, when cooling the strained stock, I put plates in the bottom of my double kitchen sink (enough to keep the stockpot from floating into the stream from the faucet,when the sink is full), then I fill the sink around the stockpot and leave the water running slowly and overflowing into the other side. This will cool the stock into the 60's within about a half hour. I then refrigerate in my beer fridge in the basement set to as cold as it will go (28 degrees, or so)
In winter, normally, I just wait for below zero weather and just cool it in a tub of snow in the garage.
This winter in tropical Minnesota, no snow, no cold, but I'm not complaining.