The Johnny Stewart sounds that I use regularly came from the same commercially available compact disks, but I don't usually use the supplied MP3's. I rip the entire cd to waves and isolate the non-repeating segments. Then after a lot of listening, I usually crop a 45-60 second clip. Then I eliminate one channel first by muting it to zero, not by mixing left and right, and reformat it to mono. If it's not fully modulated, I'll amplify it to ~95%. For an e-caller, where I use a lot of pauses during calling, I insert about a second of silence at the start/finish and then into about every 15 seconds of sound, so I have a good spot to push the caller's pause button without interrupting the sound in mid-scream and without making it a 7+ minute sequence like some of Al's. For a constant call loop, like those I use on the truck for spotlighting, I do not add pauses anywhere. Then I compress the files to 256 or 320 MBps MP3 files using the LAME codec. These files play extremely well on any caller, converted MP3 stereo, IPOD, FoxPro, Minaska, public address system, or any other MP3-capable stereo or mono system, and are approximately 3/10 the size of the stereo wave, without sacrificing a lot of fidelity to the original.
In a pinch though, I feel reasonably confident that I could replace everything I currently use with a cheap cd boom box and two or three Johnny Stewart titles and still get it done. I'd probably add a partner to make up for the lack of a remote.