[sparqee]

You compress just the send. Often times people compress the send in an extreme way and then mix it in behind the main (uncompressed track) just enough to add a kind of "thickening". It's a great way to use compression because it allows you to "add" certain qualities to a track without taking anything away. Your original track is untouched. You haven't lost any of the qualities that you typically loose when you compress with an insert. There's nothing wrong with putting a compressor on your insert, it's just a different technique. Sometimes I will do a bit of light compression on the insert and then slam the compression on the aux track. It all depends on the sound I'm after.

Another thing that can be fun to do is EQ the aux send to really highlight a particular quality of the track. Perhaps the raspy range of the voice. With extreme compression this quality (which ordinarily kind of comes and goes with vocal phrasing) becomes a more noticeable part of the voice yet still sounds natural (if not overdone).