Here's a trick I use.
I sing the main vocal part as close to a full take as I can in the beginning to see if I can capture any kind of magic that happens when you're simply in the flow of things. If I need to go back and redo a verse or chorus etc I punch those in...but continuity can be heard...you can't get that great take by punching in every other word...Once done, I double the lead vox. You can and should do this in small pieces so you can get the phrasing to match. No reason to sing this all at once, unless you really can remember what you did, and all the little embellishments, but that's hard to do...this will speed the process up greatly. After that, I sing a 3rd and 4th take...then do this.
1. Take the 2nd take (main double) and center pan this with a slight eq change and not quite as loud as the original to get it doubled. This will thicken up the part a lot. I try not to have the double as loud as the original as it softens any edge the original has.
2. I then sing 3rd and 4th parts (I know that seems like a lot but they all add up and it's worth it - even for a rapper this works, and sometimes on a rap track I'll take the parts and use a pitch transposer on a part so they aren't all the same) and add them to an aux track leaving them center panned. In the aux track I add a stereo delay and a compressor (I do have compressors on all the vocal tracks..it's the difference maker)
I then use the delay to pan the tracks (3 and 4) by taking the left side and zeroing everything out so it's has no effect, then on the right side max out the send and use a short delay around 8-12ms. This will pan everything so you now have your vocals on the left and right channels. I do this so I get both tracks panned...if you don't use an aux track and just pan the 3rd and 4th takes...it's just one voice per side...this gets both voices on both sides. (*note - psycho-acoustics being what they are...you might have to turn up the right track (say the 4th take) a little more than the left track to balance them out...our ears will hear the left track first since there is no delay and bringing up the right side volume will compensate for that...this is one of those instances where the meters do lie)
3. Once you have that done bring up the aux track with takes 3 and 4 on it so you can barely hear the voices in the left and right fields (experiment with how much you need...say a small amount on a verse and a little louder on the chorus to get the chorus fatter for dynamic reasons...
I do all the background parts this way (only using a double instead of 4 tracks...they get nice and thick)
This can be done in such a way that you don't actually hear all the parts...but when all of this is in a mix...it fattens things considerably.
Just one mans thought...Have fun
Jason216