Simple trick, using the principle of 'blurring' a wav file. Got the idea after using my new fl studio and blurring a waveform. I watched a vid on how to do this. So I recreated it in caustic.
Basically record yourself ahhing, and then normalize so the volume is low.
Then copy the whole waveform, move the cursor a bit and paste mix it.
Do this a few times and play it back, and there is a nice chorusing choir sound.
Then eq it, add effects and go wild.