Try using am omni mic in the center of a ring of people shouting the lines rather than trying to blend a bunch of single tracks to try to get the same effect.

More vocal tracks! What you should do, however, is raise the pitch of the track a half step and do another set of harmonies, raise the pitch of the track another half step (a full step above the original) and do another set of harmonies, lower the pitch of the track a half step and do another set of harmonies, lower the pitch of the track another half step (a full step below the original) and do another set of harmonies. Then put everything back into the original pitch. Do some falsetto tracks the same way, there are always women in crowds like that. This will change the tonal quality of your voice a bit giving the impression of more than one person doing the vocal harmonies. Do not make the additional performances perfect, in fact, be sloppy; a large percentage of the people in any large crowd can't sing worth a damn. Use a crowd sample, Autotune it and blend it in.

You can also try to use voice formanting instead (or in addition). Or, the obvious, just get a large group of people to perform the vocals for you. Track them multiple times using the above "trick."

Check out Roger Waters' album "Amused to Death"; on the track "What God Wants, Pt 2" there is a huge stadium crowd effect that was done using a combination of multiple singers, pitch manipulation and effects.

duplicate each track, put a slight delay on the duplicates. instant big choir.

8-)