For echo-delay, you can use audition to create the echo\delay in the audio with an effect. The bigger the delay, the bigger the separation. You can also add more voices, with splits between each voice (delay). Smaller delays sound like many voices singing in unison, while larger delays will result in a "repeat back" kind of echo.
To make a more definitive effect, dupe the audio track, then clip the area where the double effect occurs, and take it out of sync by a couple of frames (the delay). You can do this for several tracks, and even have the echoes trail and grow so they pile in mid sentence but trail off at the end if you double, then triple and quad the effect (delaying each one by a few frames from the last one)