If you want "LUSH" vocal harmonies, track each part separately (yes, have someone actually sing the part into a mic), in isolation.
Then balance/pan the tracks, and add EQ/reverb to taste.

If you're really clever, you can track them all at once, and let the bleed work for you.

I'd rather have a separate backup vocal track to work with than adding it with a harmonizer, personally.

What style of music are you doing (no familiarity w/ Crossfades)?

Thanks...brother(soapfloats)...I should go back to school and study punctuation again. I meant that I was listening to "COLORS" by the band "Crossfade"! It's your basic modern AOR type music, rock with the raspy voice thing, like Nickleback or any of 100 other rock bands out there. Ya know I really do appreciate the tracking advice and I've actually done quite a bit of it myself at my little studio that could see http://www.myspace.com/rockdawgstudios I'm just wanting to expand my personal repertoire and was looking for some advice on doing so utilizing harmonizers/voice doublers/etc. It's funny you should recommend actually singing the tracks, ask anyone around here and "I'M" usually that person...hence our reason for departing the gangsta-rap genre. It was all just becoming...Track-copy-paste-tweek....dull at best! No, this is about being able to offer something quickly, as I've learned with today's studio budgets, most bands just "CANNOT" afford to track four to six perfect vocal takes just for the purpose of harmonies. I know I'm doubling back on what I just said, unfortunately, that's an "ECONOMIC" reality in today's studios!!!

"I should go back to school and study punctuation again."

The only tip you need:
- Use the enter key sometimes. This isn't IM and enter won't send half a message.