A more effective method is to use a separate immersion chiller for the cooling water (I'm assuming you already use an IC in the boil kettle.) Use the kettle IC alone to get the wort down to 100Â° or so. Then you redirect the incoming cooling water through the second IC, which is immersed in ice water. The output from that IC (now extremely cold) goes into the primary IC in the kettle. You will drop the remaining 30Â°+ in a hurry.
Yes ... the pre-chilled ice bath is exactly what I use, just figured out how to "pre-chill" the water without using a ton of store purchased ice or having to cut open the plastic jugs each time.