If your running a duel plane manifold Denny's procedure will work good for you, but I have found it doesn't work well on an open plenum or single plane manifold. What I have found on a single plane manifold is you can close off completly on one of the circuits and the car will still pretty much idle the same especially on the four corner idle circuits carbs.
For a single plane manifold I start with all of the idle mixture screws at 2 turns open then make equal adjustments towards the closed position on each screw from there a little at a time. Use the vacuum guage method as Denny listed. One thing I have found on a larger cammed motor is I usually have to run the idle mixture a little rich with those double pumper holleys to get good throttle response, might just be me though.
One thing two if you can't get your motor to idle low enough to stay in the idle circuit as Denny mentioned you can drill a 3/32" hole in the primary throttle plates, this will get the plates back into the idle circuit.